iMac cannot update because error claims device is not connected to the internet, but it is connected?

What is the sub-model and the current macOS of your iMac? They have been in continuous production since 1998 in hundreds of variants that do not share the same update/upgrade possibilities. "About this Mac..." shows that important information:

Remember that we are other end users like you and have no means to see nor remotely access your computer to learn its specs. We rely on you for that. And we are really bad at guessing! 🥴

Ahh… OK that makes my job ( and ours ) easier

Thanks… your Retina 4K iMac can be upgraded to Catalina, per this link : macOS Catalina is compatible with these computers - Apple Support (CA)

or greater… please note that Catalina breaks all 32- bit support… all apps/software/plugins must be 100% 64-bit and Catalina compatible to work ( and yes, that does include printers)

hope this helps you

John B

Hi djolik could you tell us more about your iMac , eg, year made, model, what Mac OS is installed on it currently, etc? You can find that info by going to “About This Mac” , top left of your screen under the Apple ( 🍎) and post that here… please don’t post/ include serial numbers..

thanks ….

John B