Don't know. I searched, got a number of hits, read some suggestions, but didn't see an exact solution and explanation of the problem.
For what it's worth, see Desktop Manager Greyed Out when device connected
. Bottom line in that thread is the OP successfully upgraded the OS and all was fine.
Just as a SWAG, you might try a security wipe and then see if you can connect properly, but only if you have a backup file so that you can selectively restore your data afterwards.