Here is a problem with DNS registration for SPF and MX

[KangJL]

If you read clearly, the answer is there

Sub-subdomain is no longer supported on free hosting

Changes to SSL for free subdomains

We’ve made some exciting updates to how SSL certificates work for free subdomains on InfinityFree! These improvements simplify things for you and help us ensure our hosting platform remains fast and scalable. Here’s what’s new: SSL by Default for All Free Subdomains Good news! Every free subdomain under our supported domain names now comes with SSL enabled automatically. No need to request, install, or renew certificates yourself - we’ve got it covered! We’ve implemented a…

especially this

@Admin

No More SSL for Sub-Subdomains (e.g., blog.example.ct.ws)

Sub-subdomains—domains that look like something.example.ct.ws - will no longer support SSL. These were never officially supported and were only possible due to a bug in our system.

That bug has now been fixed. Going forward, you’ll only be able to create regular subdomains, which are fully supported and automatically secured.