There can be several possible reasons why your My Canon printer is offline. Luckily, the issue is easier to resolve than it seems. On facing such an issue, all you have to do is check 3 important things-
Check the internet connection and make sure it is stable and fast
Check that the connection between the devices, either wireless or wired is proper
Check that your printer is not set to operate in offline mode. By that I mean to check your printer settings.
Hope one of the above-mentioned solutions will help you fix the issue once and for all.