URL is not on Google

Dear Sir,
after using the RankMath, the index looks to be disturbed. i am not able to find any subpages in google search console.
while crawling in google console, it throws error “URL is not on Google”. while trying to create index error is thrown

Indexing request rejected
During live testing, indexing issues were detected with the URL
URL is not available to Google
It cannot be indexed. Learn more
Indexing allowed?No: ‘noindex’ detected in ‘robots’ meta tag

Looks like index is blocked by robot.txt. after some time spent on google, i found that robot.txt is not allowing subpages and few are telling that the issue may be because of the SEO. Since i am using this Rank Math only, i am seeking ur help.

my website is http://www.rplabs.in
subpage i am trying to index is : https://www.rplabs.in/googlead-campaign/

plz help/suggest