There is an easier way to get the exact version .NET version installed on your machine from a cmd prompt. Just follow the following instructions;

1. Open the command prompt (i.e Windows + R → type "cmd").

2. Type the following command, all on one line:

reg query "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP"

(This will list all the .NET versions.)

3. If you want to check the latest .NET 4 version.

4. Type following instruction, on a single line:

reg query "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\full" /v version


or type the following in the command line:

dir /b /ad /o-n %systemroot%\Microsoft.NET\Framework\v?.*

PDF Creator - Error-Nr: 339 (Component MSCOMCT2.OCX or one of its dependencies not correctly registered: a file is missing or invalid)

Solution:

You logged in as administrator and used pdfcreator once. After logging in as user, the problem was gone as well.

or

It looks like, registering  MSCOMCT2.OCX solves the problem without the "start as admin"-trick:

For a 64-bit OS create a batch file with 

regsvr32 C:\\Windows\\SysWOW64\\MSCOMCT2.OCX 

or for a 32-bis OS

regsvr32 C:\\Windows\\System32\\MSCOMCT2.OCX

and run the file as administrator.

Make sure you have full backups of your databases.

On the primary replica node, change the failover mode to manual

Refresh the databases and check if MSSQL reports any errors

Apply fix - CU0x service pack Perform an update for all databases until all fixes are uploaded.

After uploading patches and restarting MSSQL, check if the cluster is in good condition. P

erform an update for the Primary server.

After uploading all patches, check if the cluster is in good condition.

If there are no errors, change the switching mode from manual to automatic.

Apply SQL Server patches or cumulative updates in SQL Server Always On Availability Groups (sqlshack.com)

SQL SERVER - How to Apply Patch in AlwaysOn Availability Group Configuration? - SQL Authority with Pinal Dave