1. Please, ensure that ‘Always a high score’ mode is used while running Setup Wizard. https://www.s-sols.com/docs/wordpress/accelerator/getting-started-accel#optimization-requires-time
2. Next step, pls, ensure that all pages are optimized by launching all cache update by 'Revalidate cache if needed' in 'Operations'. https://www.s-sols.com/docs/wordpress/accelerator/status-and-operations-accel#operate. After ending optimization, pls, wait few days for improvements.
3. Ensure that server/external cache is allowed: https://www.s-sols.com/docs/wordpress/accelerator/settings-accel/settings-server-accel#general.
4. If it doesn't help please check TTFB metric in PageSpeed result. It can be additionally tested by this tool: https://speedvitals.com/ttfb-test. If it is high then issue is in hosting/server/network. It can be improved by using CDN like CloudFlare (free plan) with page caching. Here is how to setup page caching in CloudFlare. Also, it is necessary to have GZIP compression activated on your server to optimize the resources’ loading size and time. If it is not enabled on your server, then you need to contact your hosting provider for help. Check if works correctly using the following service https://www.giftofspeed.com/gzip-test/.
Also, Core Web Vitals updates once in 28 days or rarely, just wait, we can’t affect to that.