I saw an advertisement for this service on one of the crypto-related websites I visit. They promised an exchange without registration or KYC so I decided to give it a try by swapping a small amount first.
You're probably in the market for years already. You must have observed and known that it's not uncommon for advertisements to have claims that are either straight lies or at least misleading. Words like decentralized, peer-to-peer or P2P, privacy, safe, cheap, instant, secure, KYC-free, among others are often falsely used.
Just like 99% of exchanges, P2Pchange is guilty of it. You can "exchange without registration or KYC" until you cannot.
I checked quickex, they have AML policy posted on their website so it's no wonder they block transactions if the risk level is too high.
Since you've exerted a little effort checking Quickex's KYC/AML terms, did you do the same with P2Pchange, with whom you had transactions involving significant amounts?
If you didn't, then please know that they also have such terms.
[1]2.7 Anti-Money Laundering (AML) and Know Your Customer (KYC) procedures may apply. Users must provide documentation verifying identity and the origin of funds. Compliance checks may involve third-party providers adhering to our privacy guidelines.
2.8 Transactions flagged as suspicious may be paused or declined at our sole discretion.
If Quickex may block transactions, so does P2Pchange.
[1]
https://p2pchange.is/docs/terms-of-use/