Humidistat issues

[dba7108]

Just purchased a manrose humidistat from screwfix. The controls seem to make no difference and it doesn't turn the fan off. I have two fans wired off the one stat. On the screwfix website they say in the Q &A bit that this isn't possible. No idea why it wouldn't be. Any help please or do I have a faulty unit?

[speedyman]

Would be a help if you provided a link to which stat you have