Odd, try using this fix,

https://steamhost.cn/steamcommunity_com/groups/tf2outpost/discussions/0/558747922562007365/#c540742485382266453

Can you be more specific?

Are you trading on Outpost?
What exact error message are you getting?
How long have you had this error message for?

Account security reasons, did you recently log onto your account with a new device?

Seems to be a Steam related issue, can you be more specific as to what error message you get?

Game wise: scout the market for trending games, familiarize yourself with the game market of your choosing and make sure the game will have a stable sell price in the future.

Price wise: prices all depend on coverage, the better coverage you have in your games market the more flexible you can be with your buyout.

Insurance wise: just offer a ROW tradable copy of the game, you generally won't run into any skeptical or paranoid traders unless they're new.

From what I remember the strange quality doesn't give the item more value.

The item is currently priced at 8.00 refined and has a high chance of raising to a key.
If you need more guidance price check wise, feel free to add me as price checks are against the forum rules.

Item histories.

As per not specifying who and what a third party member is in this case I will persuade myself into leaving my own critique on this matter.

And that would be that this derogatory complaint is pretentious, you do no more than hide avaricious intent with a vast vocabulary, yes you may counter me by further divulging your argument but in reality this isn't a matter of injustice or an exposition of exploitation but rather a response of indignant intolerance.

In a more intelligible and short response, just let it go, this will cause nothing more than unnecessary conflict.

You can further more complain and counter how illegal it is of them, but it will in a most likely case do you no good.

Don't mistaken this for an attack, this is merely a response to your complaint.

I assume the ban is quite situation, if you are caught knowledgeably trading with a marked scammer you will not receive a warning, however, in most cases you receive up to two warnings.

That's completely up to you.