- At that time I grabbed the address in Armory by clicking on 'receive bitcoins'. However when I click that button now, another address pops up. Hence I was afraid that you can only use an address once or something.
That's how it has always worked. The code cannot know that you have not used this address (or showed it to someone else) after you request it. Therefor it will always give you a new address when you click "Receive".
- When Armory did not show the correct balance, Armory displayed no error whatsoever. Armory stated that she was online and fully synchronised. Bitcoin Core did too.
Armory itself was most likely off sync. I could tell you if you show me dbLog.txt