I use DreamHost’s DreamPress product for this website, as part of that product there are caching plugins installed. Normally this would be perfectly fine but after an upgrade that caching was preventing me from accessing the dashboard. This post explains how I got past it.
Make sure you are logged in and can see the admin bar at the top of your site. From that bar purge the page and database cache.
From the DreamPress dashboard go identify your SSH credentials and use them to login using SSH.
Once you are logged in using SSH use ‘cd yourdomain.tld’ to access your website directory and execute ‘wp cache flush’ to clear out any remaining issues.
That’s it, go ahead and try to access your dashboard again.