Hi @Suty thank you for your reply. SimonUrbanek mentioned directly in this thread, that I am not the only one who is facing the same issue and also another user (ctd_) also mentioned in this thread that the same issue occurred.
I can confirm that I am on the latest iOS and wearOS and the synchronization iphone-watch is working for the rest of the apps I am currently using.
Thank you very much for looking into this issue, I do appreciate it :)