If, like me, you have run into problems installing Avast One on MacOS 15 Sequoia where you get stuck on the Avast setup screen to allow permissions, then the following might helpl.
Go to System Settings. Scroll down to ‘Privacy and Security’ and select this. On the right hand side go to ‘Full Disk Access’ option and click into that. You should see an entry for ‘Avast One’. Turn the toggle switch to ‘ON’.
Then head to the ‘General’ item in System Settings and on the right hand side scroll down to ‘Login Items and Extensions’ (or you can search for this in Finder). Under the ‘Allow in the background’ option, make sure the toggle switch under ‘Avast One’ is set to ‘ON’.
Then scroll down to the Extensions section, and click on the ‘i’ next to ‘Network Extensions’. This should open a new window where you should see an entry for ‘Avast One’. Turn the toggle switch to ‘ON’ and then head back to the Avast One set up window.
This should have done the trick and you should see green ticks allowing you to progress to the next screens in the Avast setup window.
Hope this helps and please add anything else that would be helpful.
I’m sure the Avast team will update their program in due course (although it would have been better if this was done from day one of MacOS 15 being released).
Good luck!