Just realized... If you can log in to the DIS, and see the Boards, *AND* see my PM's to you...
... let's just have you change your email address from here!!! (I know - it still doesn't give you access to the Gmail account itself, but it solves this one part here at the DISBoards)
Go up to the top of the page, and click on your little picture that is just to the left of your Messages, your Notifications (looks like the little bell) and the SEARCH icon. Click on your icon and it should show your username and directly under that, the Gmail account.
Just change that to an email account that you *can* access. You will need your password for the DISBoards to complete this step.
Once you have entered the new email address, and your current DISBoards password, it will send you 2 emails. The first one goes to the new address you changed to, telling you that hey, you changed your email address, and to verify that, please click here on this handy-dandy button.
The second email goes to your old Gmail account that you can't access, and basically says hey... so you changed your email, just letting you know in case you didn't want that to happen.
And then you can have notifications from the DISBoards sent to your email account again and they should work fine.