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.
You are stuck on the Terms & Conditions screen
Before OneView opens, you must accept three documents. Two things commonly hold people here:
Both checkboxes are required. One covers the OneView Terms & Conditions and Privacy Policy, the other the OneStop PRA Terms and Conditions.
Each document has to be opened first. If a tab is unread, OneView names it and will not let you accept. Scroll to Bottom gets you through a long one quickly.
If you chose Decline, you were signed out on purpose. Sign in again and accept.
It says it could not verify your acceptance
The screen reads We couldn't verify your acceptance and offers Try again and Log out. This is almost always temporary. Select Try again. If it persists past a few minutes, it is not something you can fix from your side: raise it, quoting the message.
MFA is set up but not accepting codes
Check the device clock on your authenticator app; a drifted clock is the usual cause.
OneView has no security settings of its own, and neither does MyAccount. OneView's Settings covers containers, vessels and PRA; Manage Account holds your profile and contact details. If your organisation uses multi-factor sign-in, it is applied at the OneStop sign-in step itself, before OneView opens. If a code is rejected repeatedly, raise it: see Raise a support request.
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.