Do you get a specific error message whenever record your income in QuickBooks Self-Employed (QBSE)?
I'd appreciate it if you could share additional details so I provide an accurate answer for you. At this time, I suggest you open your browser's private window. This avoids the use of the cache, which is the common culprit of unexpected behavior in browsers.
Google Chrome: Ctrl + Shift + N
Microsoft Edge: Ctrl + Shift + P
Firefox: Ctrl + Shift + P
Safari: Command + Shift + N
If that works, go back to your regular browser and clear its cache. Otherwise, open a different browser that's available for you.