Here's one possibility you can check:
This is one of many acknowledged bugs that can be found in the Known Bug List here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: http://www.4shared.com/file/8orL8apk/FMP_Bugs.html
Thank you, PhilModJunk,
"server.pem" file solved my problem.
In the other post you mentioned, gnat wrote as follows;
In case it helps anyone else, perhaps the FileMaker team, there was a server.pem file in there, but it had zero KB file size. I copied another server.pem file from a working computer, which had 8 KB file size, and swapped it in.
However, in my case, server.pem file that did not work is 8KB and it looks like a proper certificate file when opening with text editor.
Anyway, after replacing this file, everything is OK!