Cheers for the reply. Sorry not sure what you mean. The same pause hotkeys work as normal in multiplayer, but fail to trigger in that specific scenario as I described.

If I pause a multiplayer game, disconnect from the server, and rejoin, the game is paused as expected.

The problem is, I cannot unpause the game using any keybinding for Pause game.
It is only possible to unpause using the Unpause game button on the Game menu