Hi,
Would it be correct to assume that you have a dual-band Wi-Fi gateway/router (with 2.4 and 5 GHz bands)? Any information about the make and exact model? Please do not post a serial number, MAC address, or any access codes.
Regarding wireless security, see also Recommended settings for Wi-Fi routers and access points - Apple Support.
At least according to the specifications at https://canoncanada.custhelp.com/app/answers/answer_view/a_id/1035453/~/specifications---mg3620, the MG3620 uses 2.4 GHz. A modern router does often have a "smart" way of detecting devices and automatically selecting bands. Sometimes, this can lead to a problem, and one may have to manually split/rename bands.
As you already know, the MG3620 is a printer supporting the AirPrint technology. You may have to try a full power-cycle sequence (including the gateway/router): Power off the gateway/router and all other devices/computers. Wait two to three minutes. Power on the gateway/router. Wait two to three minutes. Power on the printer. Wait a minute or two. Power on all other devices/computers.
About AirPrint - Apple Support
Use AirPrint to print from your iPhone or iPad - Apple Support