Gmail issue

Have similar issue I believe. I got notification that I had to go to Internet Center to change the gmail password. Except there is no place to change the password. (there should be an automatic dialog box that appears, it doesnt)

I removed the gmail account, and went through the process to add it back to the system. Username/Pass then the Auth code, then the accept dialog box. Then I get error message : "Failed to authenticate with Google, please try again later"

Quite funny right? LOL

I haven't read many people having problems with gmail - a couple of people noticed a hang when trying to sync very large accounts for the first time, but that was also reported to have been fixed in DP2.

Gmail accounts in Mail have such a history of issues that it's quite likely not connected with the fact that 10.11 is in beta.

Have you tried removing your gmail account(s) from the System Preferences > Internet Accounts, rebooting and adding them again? It quite often fixes the problem (sorry it didn't seem to for you though JimMilton).

As Max said, there are a number of threads about large GMAIL account issues. Very hard to pinpoint the underlying issue. I myself had this problem on El Cap Beta 1, raised a bug and couldn't get past it always stopping on 'Downloading Messages' even when left for 24+ hours. Onto El Cap Beta 2 and from minute 1 no issue at all with same account however couple of days on I am once again seeing it stick at 'Downloading Messages'. I would say that the issue appears more prevalent with GMAIL and Hotmail/Outlook accounts more than any other.

I have pulled rowID data and sysdiagnose and uploaded to the bug I opened to see if anything can be gleaned from that data.

In the meantime as Max said, best thing to do is removing and re-adding or another suggestion is to uncheck the 'Enable this account' option 1 by 1 (if you have more than 1 account) to try and isolate which one is causing you the issue.