The fact that they can't accept money from U.S. citizens is a big red flag. No clear explanation has been given. Raises questions that will hurt their credibility.
The prohibition doesn't depend on us, it's the US legislation that prohibits US citizens/residents to participate. We are law-abiding, so the information about this prohibition was (and is) always presented on our site in the "Documents" section. Like in this one, for ex.:
https://ins.world/INS-Agreement-on-Sale-of-Tokens.pdfIgnorance or unwillingness to read these docs or ask our 24/7 support does not exempt a person from this responsibility and is not an excuse.