Update: Apple Calendar Email Alerts

I have seen many past postings regarding Apple Calendar and Email Alerts not working. I discovered this as well. I recently bought a Macbook Air (M2), and wanted to set up Email Alerts for calendar events (whether an all-day event or specific timeframe). It worked for a short period, then stop working. After long investigation on my part, I found that if I shutdown the Macbook Air, my email alerts do not work, but if I leave the Macbook Air on, the email alerts work all the time. I am confused as I use iCloud to link all my devices; thought that was the reason for iCloud. I also notice that Email Alerts do not show up on iPhone, iPad, or iCloud.com; only on Macbook. Why? And why do I need to keep my Macbook Air on in order to get Email Alerts from Apple Calendar?