E-Newsletter Members list disappeared & unable to import

I sent out a newsletter a month ago to about 2800 people and it seemed to work fine. I had another user attempt to make a new newsletter but they accidentally edited the old newsletter. When I tried to send it, it said that all members had already received the newsletter so it would not send.

So I created a new newsletter, copied the html from the old (now updated) newsletter and pasted it into a fresh newsletter. When I tried to send that one it gave me the same error. I checked the box that said "send to all members (2800) except unsubsribed" and I even unchecked the box that said "don't send to those who already received" just to try to get it to send anything. It still won't go.

I went to check out my members list and it is showing 0 members. I tried to re-import my members list from a .csv and the screen goes blank and nothing imports.

How do I get my members list back and why is it showing 2800 members when I try to send but telling me that they already got the newsletter when it was never sent?