I'm not doing facebook traffic - mostly all seo, some youtube and my sales are going up.
In total with all my sites I'm doing just over $1k a day with clickbank alone.
Has the vendor of the product changed anything since you started promoting it?
Hope your sales come back - maybe time to test different traffic methods if you're doing paid. Personally, I hate doing paid traffic because of all the changes of TOS and new rules to keep up with.
For those saying Clickbank is shaving commissions, I highly doubt that. Vendors maybe doing shady stuff but I wouldn't solely blame clickbank.
If you do come across anything shady - report it to clickbank.
Most vendors who use email pops - I think you still get credited for the sale because your cookie should be set. The only way for them to get the sale is to add their own affiliate link or if the visitor clears their browser. I'm not 100% on that but that my thoughts of what happens.