Sync cohorts to hubspot sometimes partially sending

Hi Guys,
 

I’m having a weird issue here. What I am trying to achieve is that when users sign up to our app they trigger a `sign up` event, using this I gather them up into a cohort called `New Users` and periodically sync that to hubspot. 

But when I sync it, it creates a list but doesn’t send these users. On the history tab of the sync it says 0 users sent. Why is that?

Also to test it out I tried syncing the `New Users in the last 30 day` cohort (provided by default), and from around ~161 it only synced 13 users. 

In my destination configuration, I chose email for both hubspot and amplitude identifiers.

Could someone help me out?

Thanks