Slitherine

Oh wow, is this new? Does Slitherine know?

I am not sure, it is frustrating but I do not hear many people talking about it, which either means it is a bug that I singly have or something that no one else wants to admit happens

either one of those answers does not make me happy

It sounds very annoying. It might be time zone-related. Every now and then my work Outlook account lists emails I received 'Tomorrow'. Unfortunately that doesn't help fix the problem.
Have you tried reinstalling the game? This is ok if you have pc gold, but very tiresome if you bought the DLCs individually (i ended up buying gold during a sale so I could reinstall from time to time).

The Slitherine PBEM server is hosted in the US (the same as goose_2) as far as I know...

I could try to reinstall the game, I have considered that, but I have bought the game piece by piece and as such I do not want to invest the time to reinstall for the possibility it would fix the issue.

I have thought about buying gold just to have one code, but not yet....

For now I just play

As for the most difficult level, definitely is the Ultimate.
Then Manstein, great fun if you try to learn it though.
Guderian is not so difficult, especially in defensive maps, I tried in Grand campaign East 44 and actually liked it, to end missions earlier!
Rommel is the "easiest" of all the above, as long as manage the less prestige issues.
Field Marshall, neutral.
The player can switch difficulties at the beginning of every Grand Campaign, for me I started in 39 as General, then to FM, by 1942 I tried Manstein, 43 East Rommel, 44 East Guderian. All worked fine and had great time testing them

ps1 thanks for the survey option