Unable to install CMS database for skype for business 2015 in SQL server 2016

Have recently migrated from Lync server 2010 to Skype for business 2015. All users migrated to skype for business 2015 and as a last step trying to move the CMS database from Lync server 2010 to skype for business 2015.
As mentioned in( https://docs.microsoft.com/en-us/lyncserver/move-the-lync-server-2010-central-management-server-to-lync-server-2013 ) for CMS migration, first to install the CMS database on the skype for business 2015 FE server but while trying the (Install-CsDatabase -CentralManagementDatabase -SQLServerFQDN C01ict-SFBdb.abc.domain.com -SQLInstanceName RTC) command, getting the below error.
Now if we look into the error, it is mention that (Install-CsDatabase : Failed to connect to the SQL server C01ict-SFBdb.abc.domain.com\RTC) means unable to connect to the RTC instance. and yes the RTC instance was not in the SQL server, so we have to create the RTC instance in SQL server or have to use the install-csdatabase command without the -SQLInstanceName switch, which is an easy way. so the required database will be created in the default install of SQL server. so we change the command to (Install-CsDatabase -CentralManagementDatabase -SQLServerFQDN C01ict-SFBdb.abc.domain.com) and the below error was gone. the LIS and XDS databases were created within SQL default instance. and the issue was resolved.


Error:
Loading Modules for Skype for Business Server 2015...
PS C:\Users\User> Install-CsDatabase -CentralManagementDatabase -SQLServerFQDN C01ict-SFBdb.abc.domain.com -SQLInstance
Name RTC
****Creating DbSetupInstance for 'Microsoft.Rtc.Common.Data.XdsDatabase'****
Trying to connect to Sql Server C01ict-SFBdb.abc.domain.com\RTC. using windows authentication...
Exception Stack:
Type: System.Reflection.TargetInvocationException, Message: Exception has been thrown by the target of an invocation.
Type: Microsoft.Rtc.Common.Data.DbSetupSqlServiceNotInstalledException, Message: Failed to find SQL Service. Make sure t
hat SQL Server service (instance name RTC) is installed in machine C01ict-SFBdb.abc.domain.com
Install-CsDatabase : Failed to connect to the SQL server C01ict-SFBdb.abc.domain.com\RTC.
At line:1 char:1
+ Install-CsDatabase -CentralManagementDatabase -SQLServerFQDN C01ict-S ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:SourceCollection) [Install-CsDatabase], DbSetupSqlServiceNotInstalled
   Exception
    + FullyQualifiedErrorId : SqlConnectionFailure,Microsoft.Rtc.Management.Deployment.InstallDatabaseCmdlet
****Creating DbSetupInstance for 'Microsoft.Rtc.Common.Data.LisDatabase'****
Trying to connect to Sql Server C01ict-SFBdb.abc.domain.com\RTC. using windows authentication...
Exception Stack:
Type: System.Reflection.TargetInvocationException, Message: Exception has been thrown by the target of an invocation.
Type: Microsoft.Rtc.Common.Data.DbSetupSqlServiceNotInstalledException, Message: Failed to find SQL Service. Make sure that SQL Server service (instance name RTC) is installed in machine C01ict-SFBdb.abc.domain.com
Install-CsDatabase : Failed to connect to the SQL server C01ict-SFBdb.abc.domain.com\RTC.
At line:1 char:1
+ Install-CsDatabase -CentralManagementDatabase -SQLServerFQDN C01ict-S ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:SourceCollection) [Install-CsDatabase], DbSetupSqlServiceNotInstalled
   Exception
    + FullyQualifiedErrorId : SqlConnectionFailure,Microsoft.Rtc.Management.Deployment.InstallDatabaseCmdlet
WARNING: Install-CsDatabase failed.
WARNING: Detailed results can be found at
"C:\Users\User\AppData\Local\Temp\Install-CsDatabase-975ca94c-1c88-41bd-80e4-54e4265b8dc8.html".
PS C:\Users\User>

unable to share files through skype for business 2015 between internal and external users

Hi,
on the front end servers of Skype for business 2015, i was getting Errors/informaitons, with event IDs:  41024,41025, 41026
Event: 41024
No connectivity with one of the Web Conferencing Edge Servers.
Edge Server Machine FQDN: server1.domain.com, Port:8057
If the problem persists this event will be logged again after 20 minutes
Cause: Service may be unavailable or Network connectivity may have been compromised.


Event ID: 41025
Connection to the Web Conferencing Edge Server has succeeded
Edge Server Machine FQDN: server1.domain.com, Port:8057
Event ID: 41026
No connectivity with any of Web Conferencing Edge Servers. External Skype for Business clients cannot use Web Conferencing modality.
Cause: Service may be unavailable or Network connectivity may have been compromised.
Resolution:
Verify all Web Conferencing Edge Services in the topology are running, and network connectivity is available.

Errors:
No connectivity with one of the Web Conferencing Edge Servers.
Edge Server Machine FQDN: server1.domain.com, Port:8057
If the problem persists this event will be logged again after 20 minutes
Cause: Service may be unavailable or Network connectivity may have been compromised.

Solution:
add the following key to resolve this issue.
reg add HKLM\SOFTWARE\Microsoft\.NETFramework\v4.0.30319\System.Net.ServicePointManager.RequireCertificateEKUs /v “C:\Program Files\Skype for Business Server 2015\Web Conferencing\DataMCUSvc.exe” /t REG_DWORD /d 0 /f


After adding the above key on the front end servers and restarting the "Skype for Business server web conferencing" service, the above errors were not appearing any more and the issue of file shares etc. was resolved.

https://support.microsoft.com/en-in/help/4023993/ls-data-mcu-41026-41025-and-41024-after-may-2017-net-framework-update