.htaccess causing 500 error

I whitelist an IP but .htaccess isn’t updated. So I open it, add Allow from IP then go to my site

Internal Server Error

/apache/hosting-dir/110298/user_dirXXXXXXXXXX.com/.htaccess: Invalid command ‘{\\rtf1\\ansi\\deff0{\\fonttbl{\\f0\\fnil’, perhaps misspelled or defined by a module not included in the server configuration, referer: https://www.XXXXXXXXXXXX.com/wp-admin/admin.php?page=aiowpsec_settings&tab=tab2

I used Notepad, saved it then uploaded. Something is REALLY wrong. I have to add this IP as he is blocked BUT his IP isn’t in .htaccess.

I’m was going to deactivate AIOWPS so I could add the IP but I don’t know if your script is the problem or I’m doing wrong.

https://www.ads-software.com/plugins/all-in-one-wp-security-and-firewall/