If someone waives VA compensation to re-enlist for AD, but MEPS states he cannot rejoin, can he restart his VA compensation?

An acquaintance of mine has recently decided he would like to try and rejoin the Army after being medically discharged some years ago. I had given him information from AR 60-210 and AR 40-501 to start. Just so we could determine if he was even eligible to rejoin. The biggest question/concern he is having is he receives monthly VA Compensation. Seeing as I am not a recruiter I am unaware of how to answer, so I'm hoping someone may be able to provide me with some answers I can give him. He already know that in order to even go forward with trying to rejoin he needs a letter from the VA stating that he will waive his VA compensation while on AD. But is concerned that for some reason or another if MEPS decides/states he cannot rejoin. Can he restart his Compensation? he states that not getting it back would cause serious financial issues with his family and cant afford to give it up if he wont get back in. Additionally he received a severance check when he was discharged and has read somewhere that he may need to pay that back if he joins again. Is this true? Honestly any information would be much appreciated...I have searched for hours trying to find information to answer his questions but none of it is very clear.