Your hosting service Hostinet setup cPanel with that plug-in. We can't know how exactly they configured that system. You will need to ask them.
The error talks about a TXT record not being found. Are you trying to get a wildcard cert? Because a DNS Challenge and TXT record are required for those. If you don't need a wildcard maybe it will use the HTTP Challenge and work better.
I didn't see any support info on Hostinet website for Let's Encrypt certs. The only place they mention "free" certs is for self-signed certs. They also offer several paid certs. They may not be very helpful to you trying to get free cert with that plug-in.
That cPanel plug-in was not developed by Let's Encrypt which is offered by the ISRG. It is just the name the plug-in uses to describe what kind of cert they are getting.
I realize this does not fix your problem but I hope it helps you understand it.
In the cPanel plugin, you should be able to select the HTTP validation method, which will avoid the problems with your nameservers pointing to non-cPanel servers: