It looks like you’ve set your TXT record’s value for _acme-challenge. to the DNS validation hostname we provided.
This is means to be set as a CNAME, not a TXT record. Let’s Encrypt will follow CNAMEs and resolve the TXT record from our DNS provider.
More precisely, you need to set the following CNAME:
_acme-challenge.gluuie.com. => gluuie.com.1kxmo.flydns.net.