i have problem in my google analytics with hostnames redirects
Example, old (non)WWW to new WWW or vice-versa?
Also, with older HTTP to the new one HTTPS or vice-versa?
How is your htaccess configured, if so due to the redirects?
Do you have some errors elsewhere like Google Search Console, browser redirection, etc.?
If you changed your URL structure, it would be nice to change it either in Google Analytics property.
I have a notification of an error with redundant hosts in google analytics, that notification has appeared just after installing cloudflare on my site … it must be some problem caused by that, I have my redirect programmed well, but it seems that google does not I recognize it