Cart Error: Cannot apply selling plan to variant

I am using Recharge subscription service, when users try and add one of the Subscription Only SKUs to their cart, they receive this error:

I have not been able to find any documentation/threads on this error messages that has just started, any thoughts?

Please send your site and if your site is password protected, please send me the password. I will check it for you

Was this issue ever resolved? We’re having the same error with our own subscription app with Subsciption Only SKUs.