I was also blocked this morning. I don't often use my card with such high amounts, but when I asked the bank about the reason for those protections, they said something kind of like this (translated from French) : "This website is not known from us and as such is flagged as a potential fraud". Not sure what they would need to "know" the website in the future...

They said they could remove the ban temporary on my account to allow me to do the purchase, with a duration of my choice, but that didn't work so far. I may try again tomorrow to check if it is only a delay from the bank, or something else.

That does not help to keep confidence with the project...