Hi Welcome to JustAnswer
Can you send me its screenshot ? How do you access your gmail account ? DO you use outlook/thunderbird etc or you are using Gmail web version ?
ok. Since when this started happening ?
Which browser do you use ? Seems like the problem is with the browser. Try changing browser and see if it works
Let me know if the issue is with browser only.
If required I can remotely access your machine and help you out in it.