Stripe Token not generating in ProSite

Hi There,

I'm getting the following error when trying to upgrade a Pro Site Level through ProSite front end.

"The Stripe Token was not generated correctly. Please try again."

I have two installs that are working fine. My 3rd had been experiencing this since install. I uninstalled wordpress on the site, and started clean with the following steps:
1) Install Wordpress
2) Configure Multisite
3) Configured Network Settings
4) Installed WPMU Dashboard
5) Installed ProSites
6) Installed Edu Clean Theme
7) Set ProSite Levels and Modules/Gateways - Setting Payment Gateway of Stripe
8) Configured ProSite.
8i) Currency Settings
8ii) Went to Stripe, removed the old Webhook
8iii) Created new Webhook in Stripe (they were identical, but did it anyway)
8iv) Tested Webhook - "Test webhook sent successfully".
8v) Back in ProSites, added Test API Keys (no spaces at the start or end)
8vi) Set currency the same as Stripe
8vii) Save.
9) Created site via front end.
10) Via, tried to purchase upgraded plan using test credit card information and got the error above.
11) Checked Stripe "Events & Webhooks" and the only activity shown is that of the other sites that are working.

I've had a read of the other tickets that have been submitted around this, and they don't seem to be the problem. Tried my best to do a clean install of only required plugins & themes (and only WMPU plugins and themes), to minimise variables.

Is there any logs to see what the error is when the system returns "The Stripe Token was not generated correctly. Please try again."

Any love any advice.
Thank you!