So I received this from the theme developer:
"It's probably using a different TWIG version to us so delete the TWIG folder from the vendor file of that plugin so that it uses our version. If the plugin expects to be using the latest version of TWIG then it may not be possible to use the extension.
Sorry but we can't guarantee compatibility with every third-party plugin that might exist."
My notes:
This is the first time I've had this problem with a plugin using this theme - so two questions:
1. What version of TWIG do you use?
2. Where is the TWIG file I can delete and give this option a try?
Thanks!