Postdoc position "on hold" due to covid-19 I am currently in a job in the US (on STEM OPT). I had a postdoc offer from a large US university that was supposed to start April 16. I signed an offer letter for a two year contract. We were in the process of deciding which visa to apply for (H1/J1). 

Today I got an email from the PI (HR copied) saying she would like to put the position on hold until things settle down. I asked for a clarification on what "on hold" meant and whether the offer letter was still valid. The HR replied this (PI copied):


  As for the offer letter you signed (due to redacted’s current
  situation) please consider it void until future notice.
  
  Professor [redacted] will contact you if you are still being considered
  for the position.


This is the last communication I had with the HR or the PI.

What does this mean? Since I have the signed offer, when things do settle down, is the university legally obligated to offer the position back to me before anyone else? Or the university is formally rescinding the offer and I should just move on? Can they do that? 

EDIT: Some answers have asked about my eligibility to work in the US. For clarification: I’m in the US now, in my current status, I can work in the US till the end of May. If the university applied for an H1B (which is typically approved for non profit), I could stay in the US as long as I didn’t leave the country (in which case I would have to get a visa stamped). Things could have gotten more complicated with J1, so we did not discuss much about that.
A signed offer letter is normally a valid contract.  Usually it is the only contract document.  Only someone who has read the offer letter can give you a perfect answer to this question.

They have announced their intention to break the contract.  That is illegal unless the offer letter says otherwise.  Moving on is probably your best option.  

There are two possibilities:


The university is unable to pay you, so they are forced to do something that could potentially cause them a lot of harm in the form of bad press or litigation.
They did this voluntarily or out of incompetence, in which case the university is a bad place to work and you are lucky not to be working there.


In either case, you should look for employment elsewhere.