Do 3" tablets go bad?

Cant get my cholrine up.
Been using aqua chem 3" tablets in a floating dispenser. Previous years I just set it on full open for about the first week I open pool and rest of year 3/4 of the way close. This year been open for a month and cant get the cholrine level up. Tried different test kit also. And I even got another dispenser so 2 are in use with the tablets. Tablets left over from last year when I got from sams club. Could they go bad.
Only other change this year I added a solar panel.
Thanks for any suggestions

Please post a full set of test results for Free Chlorine, Total Chlorine, pH, Total Alkalinity, Calcium Hardness and CYA (stabilizer).

Also please post the surface of your pool (plaster, vinyl, fiberglass) and the volume in gallons (or the dimensions, average depth and shape)

Then we can get a handle on what is happening in your pool. If you have the test results from when you closed the pool, particularly the CYA level post that also....it might help!