Try wiping the cache partition on the phone and that might solve the issue. To do this, just search 'how to wipe cache partition S21' and you should find what you are looking for 😀.
If this does not work, then a factory reset may resolve this issue. Try backing up the phone to Smart Switch on a computer or to Samsung Cloud. Then, factory reset the device and afterwards, restore your data, depending on method of backup. See if this fixes the issue.
Finally, if all else fails, take it to a Samsung Store or a local repair shop and they will easily fix this problem for you 🙂. Hope this helps! 😎