Q2A script not adding + sign in URLs with whitespace in the tags or usernames. Please help to fix

Previously, my website was functioning correctly, but now I am unable to access URLs with whitespace in the tags or usernames. It appears that the Q2A script is not replacing whitespace with a plus sign (+) in the tag URLs, causing a 'Forbidden' error when trying to access those pages. How can I fix this issue?

UPDATE:
I found that htaccess option in url structure is not OK but I doubt how it automatically changed from OK to blank and I have not even changed anything on server side.

Mod rewrite options is already enabled and htaccess file is also already available with default settings.

But still first URL structure is not OK and I have the problem accessing the URL mentioned above.

Please anyone help me fix the issue.