What does "I have removed one of my email accounts" mean? Removed from where? Canceled the account with the email provider? Removed the account info from Thunderbird?

Apologies, not to clear, I removed the account from Thunderbird

Do you have the removed account forwarded to your other account at the server? If the account is not still in Thunderbird there is no way for it to check mail on that account. Even if it did it would not place the messages in a different Inbox. Just to be sure when you go to Tools-Account Settings is the old account still in the list?

Use Tools on the menu bar and not the AppMenu button. No menu bar? Press the alt key.

The removed account does not forward at the server and when I go Tools - Acc settings, the account is no longer there

I do not see how this is a Thunderbird problem then. It cannot get mail for accounts it knows nothing about.