[TYPO3] Help - Upgrade gives error - The requested URL /index.php was not found on this server.

[Sandy Matheson]

Hi,

I have just started the process of upgrading a number of our sites to
version 4 and have hit a problem on the very first one!

The BE seems to be working fine. BUT the FE produces an error:
"The requested URL /index.php was not found on this server." The
entire site is therefore not accessible.

The site was fully working in v3.8.1 and has previously been
successfully upgraded from 3.5 to 3.7 to 3.8 and then 3.8.1 and I did
not encounter anything like this on any of those upgrades.

Can anyone help me see where I have gone wrong.

Many thanks,

Sandy