Hello ,
Could you please try below couple of things.
Make sure all the services (SQL , MS Dynamics) are up and running.
Try to clear browser cache, open in different browser and try with different user account.
Reset IIS and App Pool of CRM Server.
Restart SQL and CRM server once
If it is IFD setup , Try to reset ADFS service once.
Disable the Relying party once and enable it again , update Federation Metadata.
Hope all above steps help you to get it up and accessible your deployment.
Thank you.
Abarao Bhople