How do I fix 'Not Acceptable' error on Wordpress after a software update?

My access to Wordpress is blocked with this message "Not Acceptable - an appropriate representation of the requested source could not be found on this server. This error was generated by Mod_Security."

A possible solution was to disable the VPN.

I have accessed the control centre and network panels on my mac - no info re a VPN tho there are options to connect or disconnect a VPN?

Anyone else have this problem?

[Re-Titled by Moderator]