Thank you for your quick answer. Yes I kept the default path,
C/:Program files /:Common Files /: Steinberg /: VST2 /: Eventide
I learnt that Reason only support 64bits VST.
I took this screenshot to explain :
On the left you can see the “Effects”, the one built by Propellerheads and the VST ones, Maschine and Reaktor. Eventide H910 doesn’t appear in the list.
On the right you can see that Reason really scan the right folders to look for the H910.
A little bit of a mystery here ! I’ll try to reach Propellerheads to see what’s going on.