Start with the exact sender rather than the brand label
A viewing company can use different addresses for account notices and promotions. Open a known legitimate message and inspect its sender before changing Gmail settings. Google documents that blocking an address sends future mail from it to Spam. On a computer, the Filters and Blocked Addresses settings provide a way to review the blocked list even when an old message is hard to find.
Unsubscribing addresses a different problem
Google’s unsubscribe guidance concerns promotional messages and newsletters. Some senders direct you to their website, and mailing-list changes can take a few days. Removing an address from Gmail’s blocked list therefore does not itself ask that sender to add you back to its newsletter. Conversely, joining a mailing list does not resolve an address that Gmail is still blocking.
Use a narrow test for the message you actually need
If an expected account notice is missing, first check whether its known sender is blocked and whether a legitimate message has reached Spam. Avoid repeatedly signing up with different email addresses; that can create multiple profiles while leaving the original delivery issue unresolved. For promotional preferences, use the real sender’s account page rather than an unsolicited lookalike link. Keep a short note of the address reviewed and the preference changed so a later support request describes the actual issue instead of saying that all email is broken.
Questions, answered
Will Gmail’s Unblock button rejoin a sender’s mailing list?
It changes Gmail’s treatment of that sender; the sender’s subscription preference is a separate control.