Hi. Sorry you’re having this issue.
You have a Personal license for PRO (i.e. 1 site).
You can run it in the environment you described (multisite WP install with 1 site)
As far as network-activated, I believe a non-Multisite-specific license should only be activated at the single-site level, not at the network level, but I’m uncertain if it really matters. I would suggest trying that to see if it works for you.
If it doesn’t help (it may not matter if network-activated and it really should NOT be affecting your ability to enter data like a price field), then I’d ask you to please follow our Testing for Conflicts Guide and see if that helps narrow down the cause of this.
Let us know what you find out.
Thanks.