test doesn’t run

On my frontend (https://bluvacanze.it/) newsletter form always remain in “sending request”. Right now i’ve enabled debug and no ip validation.
On maintenance panel i don’t have any error evidence.

On my backend also test button has no action, i click on it but no error, no success.

my site is running on 5.7.2, i try it also on an old version 5.6.4 but same effects.

please any suggestions?

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