I appreciate that you fixed the problem with an update.
Since your theme and plugin do not use the regular WordPress update mechanism, it was not apparent that there was an update.
I have used wordpress on many sites for many years. It is very rare that an update breaks a plugin and makes the site dysfunctional like this did.
So to respond to your “for the future we recommend updating to the latest versions,” as a former software developer, I recommend to you that when updates are made, they do not break existing configurations. This causes all sorts of headaches for everyone.