The app tells you which it is. Here they are, commonest first.
1. You are not signed in
Watching needs no account; bidding does. A phone number and a code, two minutes. Can I watch without an account?
2. Your bidding is paused by strikes
The message names it: bidding is paused because wins were not paid for, and it tells you the date it opens again.
Three strikes inside ninety days does this. The window rolls, so old ones fall out.
You can ask for a strike to be removed, and the message says so. A failed card, a lost phone, a week in hospital — these are lifted more often than people expect. What is a strike?
3. It is your own item
The app refuses a bid from the seller on their own listing. If you run a store and are signed into it, that is why. Can a seller bid on their own items?
4. The store has blocked you
A store can block a buyer from its own listings. That is their right, it applies to that store only, and you can buy anywhere else.
5. The auction is not open
Either it has ended, or it has not started. If it has not started, a pre-bid may be available instead — the app will say so.
6. Your bid was below the increment
Not a block, but it looks like one: a bid has to clear the current price by at least one step. Tap the amount the app offers rather than typing a number. What is an increment?
What is never the reason
How new your account is. There is no waiting period.
How much you have spent. No tier gates bidding.
A review you left. A seller cannot retaliate that way; blocking you from their own store is the limit of it.
If none of these fits
It is probably the connection rather than a rule — a bid that does not land looks identical to one refused. My bid did not go through
And if the message genuinely does not match any of these, raise it under Account & login with what it said. How to raise an issue
The one worth acting on today
If it is strikes, ask. People sit out ninety days without ever using the route that is on the message itself. Can I appeal a decision?
More: what is a strike, my bid did not go through, what happens if I do not pay.