iPhone 16 IOS 18 mail search results not showing more than 1 or 2 out if way more

iOS 18. iPhone 16. I can receive and send mail normally. No problem.

The issue is when searching for email subjects, there are a little or no results. I know for sure that I have many results for a specific topic especially when dealing with my website.

I'm getting this message:

"Some Results May Not Appear. Mail downloads and organizes messages when iPhone is locked, charging, and connected to Wi-Fi. Large accounts like this may take longer."

I've always been able to search email and get many results all along until recently.

My phone has been locked, charging and connected to Wi-Fi all the time when I'm not taking it outside. Nothing changes.

I've done force restarts and have the latest iOS.

Any advice, please? Thanks!