Firebase Auth Couldn't Verify Domain

I also was unable to verify my custom domain for the auth templates.

My solution was to remove my custom domain from the host name in the DNS records needed for the verification.

Example:

TXT record: from contoso.com to @

CNAME record: from firebase._domainkey.contoso.com to firebase._domainkey

Note: My domain is hosted by Godaddy.com

For those using Cloudflare. Make sure you don't have DNS flattening activated in the CNAME.

Maybe the trailing space on your TXT record?

$ dig txt thewhozoo.com

; <<>> DiG 9.8.3-P1 <<>> txt thewhozoo.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 59407
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;thewhozoo.com.         IN  TXT

;; ANSWER SECTION:
thewhozoo.com.      3600    IN  TXT "firebase=thewhozoo-143913 "
thewhozoo.com.      3600    IN  TXT "v=spf1 include:_spf.firebasemail.com ~all "

;; Query time: 45 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: Thu Jun  8 23:49:07 2017
;; MSG SIZE  rcvd: 125