I am having the same issue... Started happening about a month ago after upgrading to v5 of the mobile apps...
Now I am getting this message regularly, even if I don't make any changes..
For example..
Today I added a new title by inserting a disc into my computer. It created the movie profile as expected. I then noticed that it grabbed the wrong version... it grabbed 4K instead of Blu-Ray... So i right click on the title, select Change Title Source and Data. The search popup appears, I select the proper title from the list and then save it.. And a message will popup stating:
The title could not be changed "The online service could not be contacted" The change have been aborted, please try again later.
At this point I have tried again and it still fails...
In the sync log it states:
2025-01-16 09:27:04 . 05 - Calls.AddTitle - movie added online which isn't added on client. This shouldn't happen. Title: '062b639d-47fc-4864-987f-c2f8d98ded43' - Movie '85003acc-f97b-48d8-9cdd-913a452d42bd'.
In the logs, I am seeing this message regularly..
2025-01-16 09:34:05 . 30 - Common.OnlineService.Calls.ReplaceTitle - Getting language and country settings.
2025-01-16 09:34:05 . 30 - Common.OnlineService.Calls.ReplaceTitle - Calling 'ReplaceTitleInCollection', attempt 1 of 3.
2025-01-16 09:34:05 . 59 - Common.OnlineService.Calls.ReplaceTitle - Error calling 'ReplaceTitleInCollection': System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> System.InvalidCastException: Operator '=' is not defined for type 'DBNull' and string "UPDATE".
at Microsoft.VisualBasic.CompilerServices.Operators.ConditionalCompareObjectEqual(Object Left, Object Right, Boolean TextCompare)
at My_Movies_API.DataService.ReplaceTitleInCollection(String HandShake, String UserName, String Password, String TitleId, String NewTitleId, String Country, String LanguageCode, Int32 Locale) in \\Mac\Home\Documents\Visual Studio 2019\Projects\My Movies API\DataService.vb

ine 7156
at My_Movies_API.MyMoviesWS.ReplaceTitleInCollection(String HandShake, String UserName, String Password, String TitleId, String NewTitleId, String Country, String LanguageCode, Int32 Locale) in \\Mac\Home\Documents\Visual Studio 2019\Projects\My Movies API\Default.asmx.vb

ine 1257
--- End of inner exception stack trace ---
at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)
at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
at MyMovies.API.Common.MyMoviesWS.ReplaceTitleInCollection(String HandShake, String UserName, String Password, String TitleId, String NewTitleId, String Country, String LanguageCode, Int32 Locale) in Y:\Documents\Visual Studio 2019\Projects\My Movies for WMC and CM 5.10\My Movies Common\Web References\API.Common\Reference.vb

ine 11857
at MyMovies.OnlineService.Calls.ReplaceTitle(String strPriorWebServiceId, String strNewWebServiceId, String& strResponseMessage, SqlConnection objConn, SqlTransaction objTransaction) in Y:\Documents\Visual Studio 2019\Projects\My Movies for WMC and CM 5.10\My Movies Common\OnlineService\Calls.vb

ine 3939