Hi @maportugal,
Here Hostinger panel stops working means you can not autologin or update plugin etc functionality stops working.
Can you please enable the debug log and let me know if any error.
If AIOS firewall settings making issue it might be certain funcationality stops working.
Please try disable one by one below settings if enabled and cross check if any making issue.
1) REST API – WP Security > Firewall > WP REST API Can you please cross check the Disallow unauthorized REST requests:
2) Deny bad query string – WP Security > Firewall > PHP rules tab. Deny bad query strings: uncheck the checkbox and save
3) Advanced char filter – WP Security > Firewall > PHP rules tab. Enable advanced character string filter :uncheck the checkbox and save
4) 5g firewall rules – WP Security > Firewall > 6G Blacklist firewall rules tab. Enable legacy 5G firewall protection uncheck the checkbox and save
5) 6g firewall rules – WP Security > Firewall > 6G Blacklist firewall rules tab. Enable 6G firewall rules – uncheck the checkbox and save
6) WP Security > Firewall > Internet bots ban – Blank HTTP headers Ban POST requests that have a blank user-agent and referer
Regards