message sending error

Hello !
I’ve got a problem on one of my forms.
Curiously, it was successfully tested last friday but now I get an error message on frontend : “an error occured, please try again later”.
Even more curiously : another form is displayed there : https://haut-poitou.fr/contact/ and it works perfectly, so it won’t be a server or spam issue, I think.
Even, even more curiously : if I try as admin, form works. If I use a standard account, it doesn’t.
Any idea ?
Thanks !

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