The EIN Confirmation Letter can fail to verify for a number of reasons. Please check against these specifications and try re-submitting if your letter is invalid.
A one-page document. Any documents longer than one page will be invalid.
Legal Business Name and Address match what you put in the dashboard.
The document is either a CP 757 or 147c, with an IRS letterhead.
If you do not have either of these documents, see how to retrieve one here.