Paid Memberships Pro not working on subsite

Hello,

If anybody can help please do. I am running a multisite with subdomains like
subdomain.maindomain.com and I have Paid Memberships Pro installed as a
membership plugin.
On the main domain the shortcodes from PMPro are working perfectly.
On the subsite(which is mapped to a domain) in particular post type,
the shortcodes [membership level=”1,3,5,7″]content[/membership]
is not outputting the protected content.
Any idea how to fix this?

Many thanks!