Nicholas,
It's a Google, not a GAM, problem. (Well, actually, Google has made it your problem.)
The number of scopes that GAM uses exceeds the ability of Google to correctly process them and, so far, they're not offering up a fix.
GAM 3.62 uses a new scope to process Resource Calendars, that put it over the limit, so by default, it disables the Notification Directory scope.
For now, pick your least used scope, Notification Directory and Site Verification are likely choices and disable one of them.
The Nofification Directory scope enables these commands:
gam update notification|notifications [(id all)|(id <NotificationID>)*] unread|read
gam delete notification|notifications [(id all)|(id <NotificationID>)*]
gam info notification|notifications [unreadonly]
The Site Verification scope enables these commands:
gam create verify|verification <DomainName>
gam update verify|verification <DomainName> cname|txt|text|site|file
gam info verify|verification
You might actually read the notifications from Google, so you might want to leave that one on.
As you should have already verified your domain name, this is my choice to eliminate.
Ross