Is it appropriate to apply for the same job twice if it's re-advertised? Last month, I saw a job offer and applied for it. I did not hear back from them, but it is not uncommon to wait for 1-2 months before hearing back (especially with the COVID-19 situation).  The deadline for applications closed on 17 Sept (offer was only open 1 week).  Today, I just saw the exact same job (same reference number, job description, location, etc.) advertised again.
I assume that they did not consider any of the initial applicants suitable. My question is, should I apply again? I have read advice elsewhere (e.g. here) to apply again, maybe after modifying your CV and cover letter.
Please note that I am well qualified for the position (qualifications and academia experience) and did not receive any rejection letter from the first offer (otherwise I wouldn't bother re-applying). The fact they are re-advertising suggests they are (more) desperate to find someone to fulfil that role, and might be more receptive.
Note there are some similar questions on this site (e.g. here) but not quite the same situation.  This question is specifically about seeing a job offer that has closed, and the same job being re-advertised.
Give them a call. Only they know if/why they rejected you the first time or simply didn't get to your application.
It might be good to consider the channels through which you've seen the application both times. If the first time was through the institute's official website, and the second time through a third party source, it may be that the third party didn't know the job ad was filled.