If your clients site is on WP Engine and you’re using the Free Client Site plugin, you may encounter some issues with Project Access Linkswithout cache exclusions being added. This is due to aggressive page caching (which is a good thing!), but it can be easily resolved by requesting that WP Engine setup a special cache exception.
To do this, simply submit a support ticket to WP Engine via their support portal and ask them to add an exclusion for the access token cookie.
To make things really easy for you, feel free to copy and paste this sample ticket:
My site runs the ProjectHuddle client site plugin and we need to bypass varnish caching for their cookie. The ProjectHuddle team has instructed us to ask you to place a cache exception for their cookie.
Could you please bypass varnish caching for the ph_access_token cookie?