Orders get stuck on “on hold” status (Paypal payments)

Hi all

We are using the build in Paypal method.
Orders are getting stuck on “on hold” status.

might be an IPN issue?
I entered this into the IPN url field: https://www.domain.com/?wc-api=WC_Gateway_Paypal

also, i tried testing it using the IPN simulator, but it didnt work – maybe i had the wrong settings? can someone clarify for me please, what settings to use for this?

IS there any other reason orders might remain “on hold”?

Thanks