Are all browsers affected?
Hi Levi Pedro Marcelino Matlombe,
Thank you for reaching out to Sophos Community.
Can you please share the current running firmware version on the firewall?
Did you try using a different browser such as Chrome or Firefox? It seems like a browser-related issue.
In any case, you could also try upgrading to 17.5.15 or 18 MR4 if the issue persists.