Hi!
Just received this answer in my email:
"Hi,
We are sorry for the trouble.
For an unknown reason this problem happens since January 2nd, our team is working on it to fix it ASAP.
In the mean time here is a way to launch Substance Designer anyway:
right-click-->use the "run compatibility test" and then "test program"
Happy new year!
Nicolas".
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EDIT:
I can't find this option "run compatibility test", but I changed my date to january 1, and it works...