You cannot get into OneView, or you were in and got thrown out. Work down the list.
You were signed in and got signed out
Sessions expire for security. If you keep OneView open as a day-long dashboard, an expired session can also show as Failed to load containers instead of a sign-in screen. Refresh the page and sign in again; work in OneView itself is not lost by an expiry.
Your password does not work
First check you are signing in with your username, not your email address: the Username field wants the OneStop username printed in your invitation email.
If you have never signed in, use the password your organisation admin created for you. Otherwise select Reset password on the sign-in screen. The email arrives from the sign-in service; give it a few minutes and check spam before retrying.
Your invitation link does not work
Invitations expire. Ask your organisation admin to send a fresh one.
MFA is set up but not accepting codes
Check the device clock on your authenticator app; a drifted clock is the usual cause. Set up multifactor authentication under Settings, Account Setup is where MFA is managed once you are in.
None of that worked
Your organisation admin can see whether your account is active and re-invite or unlock where the fix is theirs. If it needs OneStop, raise it: see Raise a support request. Say what the screen shows, exactly, quoting its message word for word; a rejected password and an endless spinner have different causes.