Google advises that site owners using Google Tag Manager may need to re-verify ownership of their site in Search Console.

An issue was recently detected with the Google Tag Manager verification method in Search Console, which Google confirms has since been fixed. Apparently, that issue led to sites losing their verified status in Search Console, though exactly why that happened is unknown.

Google was short on details other than to say the problem has been solved, and Read more https://techevangelistseo.com/google-search-console-fixes-issue-with-tag-manager-sites-may-need-to-re-verify/