I am unable to save and it says We're sorry-there was a problem. One of items associated with this entity is no longer valid.

Welcome to the Community, @moses4.

I've got you covered, and let's work this out so you can complete your tasks in QuickBooks Online (QBO).

Before we do so, can you tell me more about your concern?  What are you trying to save in your QBO account? Are you using a mobile phone or via browser? This way, I can provide you the most accurate resolution to your query.

We'll be looking forward for your reply. Take care and have a good one!