Fatal error related to Pro Sites PayPal express - Can't access plugins

Ugh! Where to start?
I have been experiencing problems while trying to access the network plugins page for some time but usually I would ultimately connect to it. This morning, I was updating your WPMUdev Dashboard plugin and the process did not finish. I now cannot access the plugins page at all!!

Checking the error logs, I have found the following error:
[05-Feb-2017 20:11:22 UTC] PHP Fatal error: Call to undefined method ProSites::get_profile_id() in /home/fg9aw0px4s6b7os0/public_html/wp-content/plugins/pro-sites/pro-sites-files/gateways/gateway-paypal-express-pro.php on line 3146

I cannot provide you access because the WPMUdev Dashboard plugin did not re-activate and as I said, I cannot access the plugins page.