Check if he has logged on since you last messaged him. If he ahsn't, nothing wrong in asking in the Forums if anyone knows what is up; he may be ill or have a family emergency to deal with. We have even had someone who had died here. If he has logged on and you have tried to communicate with the person with 2 or 3 messages be it in the transaction or outright messaged him and he has not responded, then I would say it is time to leave negative feedback.
We have had too many in the recent couple of years who have scammed som eof themembers here. Also nothing wrong in making it public here in the Forums. If he sees it, he then has the chance to explain himself.
Bruno
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Check my Profile page to see my 2023 Goals and my Lists of sets near completion (5 cards or less) or sets getting close (less than 100 cards missing and 75% complete).
https://www.tcdb.com/Forum.cfm/Page/B/ID/0/?MODE=VIEW&ThreadID=25745&C=0