I would recommend running a positive control for your protein of interest to start, consult the data sheet or the tissue atlas for this. Could be a few things, has the primary antibody for your target been re-used a few times or have you been making up fresh? Maybe try a lower dilution, I've found in some extreme cases i've had to go down to a 1:50 or 1:100 dilution. A lot of companies also offer replacement/alternative or refund if the antibody is not working as specified on the data sheet, so might be worth getting on to them and seeing can they give you a new batch. Also how many proteins are you probing for, if you are constantly stripping and reprobing, could be causing issues, not always necessary to strip unless the protein of interest and control are of very similar size? Could also be your secondary antibody, ECL or the developing reagent for the X-ray machine itself or even the x-ray film, is there anyone else in your lab who you may be able to borrow reagent/secondaries to test out? Or is there a Cold Capture device somewhere, these are largely replacing X-ray film. Also could be an issue with the transfer itself maybe? Can stain the membrane with Ponceau S to check or try a different Transfer Rig if one is available, try running also with fresh transfer buffer if it isn't changed regularly. What size is the protein of interest you are looking at, are you using 0.2uM membranes or 0.45uM? You may need to adjust the transfer buffer composition and transfer time depending on whether it is a very large or very small protein. Also what way are you quantifying your protein samples, BCA or something else, if you have been re-using the samples also for mutliple blots it's possible the concentration may be less than what you started with, so may need to re-measure the concentration?