To start, I’d be wary of what’s found on the internet. It’s one thing to do a little research, but it’s another thing to buy into the words of conspiratorial strangers so fervently.
No, using the game’s built in cheat codes is not a violation of any rules, thus will not result in account penalties. Therefore, something else is going on.
Based off your wording, there’s been a decent lapse since you last played. In the vast majority of these cases, it’s a matter of logging into the wrong Battlenet account, meaning an account that doesn’t have Remastered purchased. Look around for any other Battlenet accounts you have and try those.
If you can’t find it, submit a support ticket so that a GM can help search around for any other associated accounts.