For me, the round number area is strong defense level in general and if price tried to break more than once and failed, I'd consider taking profit. On the 1-min you can see a failed flag pattern around 9:45 - 9:50. That's usually good for decent counter-run and possible reversal.
I realized later that you're question wasn't about when to exit, but when the trade is invalid. I can't help you there, because of the timing of your entry. I'd have waited longer before shorting.
PA trades are typically predicated on a signal within context …, specifically taken on the supporting PA of said signal (I'm discounting momo / time & volume entries here) A trade becomes invalidated when that signal is no longer valid – and / or – the context in which the trade was taken is breached Some examples of where a trade would break down Trading a range; long the bottom / short the top Breakdown = breach of the top…, on a short / breach of the bottom…, on a long BO up; breakdown = breach of the upper range BO down; breakdown = breach of the lower range BO PB to the top…, or 50% level of a range / BO PB to the bottom…, or 50% level of a range breakdown = breach of the the level price PB to (recall we don't enter on the PB - rather the PA supporting the PB has ceased and the BO move resuming) Note Need to be careful with above stop placements – sometimes liquidity pools are created only to then be exploited - dem bastards Trading a DT; breakdown = breach of the DT - or possibly the subsequent LHs depending on entry Trading a DB; breakdown = breach of the DB - or possibly the subsequent HLs depending on entry 123 reversal; breakdown = the breach of TL made from the 3rd leg HL / LHs…, or…, breach of the 50%** level of the 1st leg (** 50% not always an exact – as the strength of the reversal varies - this is trading after all not science)…, or breach of the previous L or H (just prior to leg 1) – just depends on where the entry occurs Trend (LH / HL); breakdown = breach of the TL Trend PB; breakdown = breach of the PB range counter to original direction.., or.., breach of the TL price pulling back to Close of 1 bar / open of the next; breakdown = breach of the L…, or H of the bar just closed - okay so I included 1 timed entry - but it could also be a form of a range / trend on a higher TF Need more examples – say the word RN