Today my Indesign will not open any files. I just used it yesterday. I am on a macbook pro and Mohave. I do not have enough memory to update to Monterey. I do not know if that is the issue. I am looking for a work around as I have a couple big projects in the works. Thank you
Mojave (macOS 10.14.6) should work for InDesign 2021. How much RAM do you have installed? 4 Gb RAM required, 16 Gb recommended.
But if you used it yesterday, you should be OK. (1) Try shutting down your computer, then restart again. (2) If it still doesn't work, try restoring your InDesign preferences and caches. Here are some good instructions: