If the same issue persists, you might be experiencing some hiccups with the browser. 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.
Let's try a couple of steps to see if this is the case:
Google Chrome: press Ctrl + Shift + N
Mozilla Firefox: press Ctrl + Shift + P
Internet Explorer: press Ctrl + Shift + P
Safari: press Command + Shift + N
After that, try logging into your QuickBooks Online account, then recreate a check. If it works, go back to your regular browser and clear its cache to remove temporary internet files.