Retrograde from Catalina to Mojave. App Store link not working.

Apple support is very reluctant to have users retrograde from Catalina, but unfortunately I need to.

They provided a an App store link to Mojave but it doesn't work.

I'm logged in but still get the following message:

[Cannot Connect to App Store]

I do not use time machine and need to install Mojave - where can I get the install file?

Apple support is not viable as the only contact I am offered is to call them & to date, their help has been fruitless.