Apple mail won't log in to gmail account from High Sierra. Cannot add Google account

Call the computer Elf. Elf runs High Sierra. This machine is locked at High Sierra because this is the latest version that will run Aperture, with something like 150,000 photos. Apple mail will no longer log into Gmail. Error cited is: Curriously, Elf's Apple Mail can open a different gmail account. On another machine also running High Sierra (I don't like apple mail) I deleted all Internet accounts in System Preferences, then tried to create a new google account. A look at Console, and a search for "certificate" showed: com.apple.preferences.internetaccounts.remoteservice Failed to properly identify Apple's EV certificate. Cancelling. I may be stuck by our unwillingness to upgrade from High Sierra. Which means that we used a different platform for reading email. Currently I use the web interface, which with it's support for labels I find useful. But my wife prefers the Apple mail interface. However she can log in on a delegated account we use for business. I don't understand how that works internally.