Is an employer forced unpaid leave of absence Legal

Worked for an employer, based out of San Diego, CA since 08/19, as a full time employee, providing Quality assurance duties assisting a Federal government team, managing a contract at Wake Island, Pacific Ocean for the US Air force. Since I got back from my first tour from the island on 1-19-20, work has not started yet and is pending from the General Contractor to get all necessary requirements in place. Seems that by the time it has passes since my first tour, my current employer says they cannot pay me on a bi weekly basis anymore and I will need to use my Accrued vacation/sick time to pay for my time and after it runs out, I will get no more payments from them. Is this action legal? Does this means I'm being fired? Thanks in advance