Most failed logins come from a typo in the email or password. Retype both slowly instead of trusting autofill. If the details look right but the form still rejects them, check whether Caps Lock is on, because passwords are case-sensitive.
A reset link that no longer works has usually expired, and requesting a fresh one solves it. When the form freezes or reloads without logging you in, the browser may be blocking cookies, so allow them for the Nonnaspin site and try again. An account that is still waiting for email confirmation or verification can also be held back. If none of this helps, live chat support can look at the account directly.