The problem is not with your search expression, which works fine, but the fact that the exact string 'CERT' is not present in your cell array.
>>double(s{7, 2})
ans =
67 69 82 84 160 160
Notice the two 160 characters at the end of the string ([67 69 82 84] are the character codes for CERT). In my version of matlab, char(160) renders as a blank space (depending on your locale it may render differently).
In fact, if you look through your whole matrix, there are a fair number of strings where the character 160 appears. It seems that it's the only character outside the ASCII range, as well:
cellfun(@(s) double(s(s>127)), text, 'UniformOutput', false) %show characters outside ASCII
Probably, the simplest thing is to remove these characters (which I assume you did not want in the first place):
text = cellfun(@(s) s(s<128), text, 'UniformOutput', false);
Your search expression will then work:
>>[row, col] = find(cellfun(@(s) strcmp(s, 'CERT'), text))
row =
7
col =
2
