Hello,
I have the same problem on my site. The variation dropdown not respond for mouse click, cannot select the variations.
As soon as I open the Inspector in the browser, the field will respond for mouse click, and the options will be displayed and selectable. There is no error message in the inspector. (Safari & Chrome are same).
For your question regarding blank prices, I have prices as 0 (zero) for all variations, as I using WooCommerce and your plugin for RFQ, and quotes are sent from our CRM, not from the site. So there are no blank prices.
I also can confirm that 1.9.55 works fine…
I hope this info will help you to find the problem, and I can update to the latest version.
Thank you,