If you set a maximum and the item sold below it, nothing went wrong. That is the feature doing exactly what it promises.
What a maximum bid actually does
You name the most you are willing to pay. Metzee then bids for you: the smallest step that keeps you on top, never more, and never past your number.
So a maximum of ₹5,000 against an under-bidder who stopped at ₹2,600 wins it at one step above ₹2,600 — not at ₹5,000. You paid what it took to win, not what you were prepared to lose.
A maximum is a ceiling, not a bid. What a maximum bid is.
If you did not set a maximum
Then one of two other things happened.
The increment rounded it. Bids move in steps. The final price is the last valid step, which can sit below a number you had in your head.
A bid above yours was withdrawn or disqualified. Rare, and it leaves the item with the next valid bid — which may be yours, at your amount, while the higher number has gone.
The part that surprises people
You cannot see anyone else's maximum, and nobody can see yours — not other buyers, not the seller. That is the point: a revealed ceiling is a ceiling someone bids up to.
It is also why a maximum cannot be lowered once set. It has already done its bidding on your behalf, and unwinding that would mean unwinding bids other people answered. You can raise it.
The mistake to avoid
Setting a maximum you do not mean. It is a commitment, and if somebody pushes you to it, you pay it.
Set the number at which you would genuinely rather lose the item. Then stop watching, because the whole value of a maximum is that it bids without you.
More: how auctions find a price, how bidding works, what a pre-bid is.