In my time as a photographer I have owned several selenium cell meters - six or more Weston Masters and one Sekonic.
You must accept that they are cantankerous things and subject to either malfunctioning at times or, given their age, not functioning at all.
I have three Weston Master Vs from the early 1960s. One no longer works. Another works when given a light tap but shortly after goes back into a long sleep until the next tap. The third works and reads 85%-90% accurately.
I have a Weston Master III from 1952 or 1953. It works consistently but reads about 75%-80% accurately and even then only in bright day. Also a Weston Master II from antiquity which goes on reading but I do not trust it as it is all over the place. I carry the II and the III around my neck and match the exposures. About half the time the II is reasonably (say 60%) accurate. Okay for black-and-white and color negative but it is not one I would care to be working with in a pro photo session.
I have several Gossen battery operated meters as well. All are accurate, but this thread is not about these, so I will say no more.
It may be something as simple as a loose wire which MAY be fixable if you go about it carefully. Opening a selenium cell meter is an activity fraught with danger. Small springs can easily leap out and even if you can find them again, trying to figure out where the heck they go in the meter would be almost impossible.
Or it may be 'expired' and a display item on your shelf queen cabinet.
SO you takes your chances. Fortunately, Sekonics are not really expensive on the secondhand market. Westons are literally being given away.