If you need to upgrade PHP version, do the following:

1. Update FreeScout to the latest version.

2. Upgrade PHP to the new version.

3. Try to clear the cache using php artisan freescout:clear-cache console command or via https://your-freescout.com/tools.php script (read more).

4. Now if FreeScout does no open showing an error, manually delete all the files from bootstrap/cache, /storage/framework/cache/data and /storage/framework/views and repeat step 3)