What are the pitfalls when buying an ssl certificate?

Question

Digital certificates

Hello!
We want to buy an ssl certificate for 1cloud - Comodo PositiveSSL Wildcard
But the fact is that, as far as I understand, Comodo is now called Sectigo.
The 1cloud site is marked as untrusted in my chrome. certificate invalid:
the root certificate is not trusted;
this certificate was signed by an untrusted issuer.
In this connection, questions arise:
will it not turn out that the purchased Comodo certificate will be invalid for many users?
what could be causing this error with this particular site? (Chrome latest version)
How do you see 1cloud.ru - reliable or not? (for some reason everything is ok on my phone in chrome)
what other pitfalls can there be when buying a certificate?