How to get Youtube channel to review my products?

Are the chaneles from your niche?

Keep contacting them and with time somebody will accept

Not all will reply. If you are established and well known then you will find people get easily interested. It also happens with the same when you outreach to build links. Response rate is very low. You have to keep asking more channels. After having one or two channels reviewed your product, if you mention that with links in future request, response will be better.