Multisite problem with Cloudflare

Good morning everyone
I have a serious problem. Basically I created a Multisite site on siteground, then I activated Cloudflare, so far everything normal.

The problem starts when I go to the site, works with www, while network pannel and which is a subfolder doesn’t work in www. What do you advise me to do? have I been looking for a way on the internet for 2 hours to solve? having www is essential? for seo you think www is important and therefore I have to solve this problem, or I remove the www from the whole site, the site was created a few days ago so I have no problems: I recommend everything thank you very much

That comes straight from your server I am afraid and you need to fix this there. That is not Cloudflare related.