I'm here to help assist you with entering and saving bill transaction in QuickBooks Online (QBO).
There hasn't been other reports of users being unable to enter or save bill today. Any transactions you create in QBO should save right-away once you click that button.
It's possible that you might also be experiencing some browser hiccups. Once you visit a website, the cache will store the information which can take up space on the computer's memory. If it's overloaded, it can cause unexpected results.
In cases like that, you'll want to perform some basic troubleshooting. Start with logging into your account through a private browser: