Can I upgrade the OS of my iMac, late 2013
I have a perfectly working iMac (27-inch, Late 2013) with macOS Catalina Version 10.15.7
I cannot load some apps anymore (WhatsApp) unless I upgrade the OS. When checking for updates I get :"Your Mac is up to date". I am basically not allowed to upgrade, and doubt it is because the machine cannot run the upgrades. the iMac has 3.5GHz quad-core Intel Core i7, which is 64 bit. So I see no reason why I could not upgrade the OS.
I am worried that what happened to my first iPad will happen again, not letting me update the OS and then not allowing me to update the apps, and then not allowing me to run the "obsolete"apps. Forcing me to buy a new computer while this one is fine. Tell me I am wrong and there is a way to upgrade the OS.
Thanks
iMac 27″, macOS 10.15