Confirmations only appear if another Gravity form is completed first [RESOLVED]

I have a gravity form with a text confirmation that is inside a modal (pop up).
If I complete the form and press the submit button, the entry is captured and the notification sent, but the confirmation doesn’t appear and it looks as though the form doesn’t work.
However, if I use exactly the same form on a page that has a different Gravity form included in the content (not in a modal), and complete that form first then the confirmation works (very important - if I don’t complete the other form and submit it and receive confirmation it doesn’t work).
Do I need to do something to initialise Gravity Forms on the page if the form is in a modal?
Thank you.

This issue is now resolved after contacting Gravity Forms Support. It was caused by caching through the WP Rocket plugin. To resolve the pages that included the forms have been excluded from the cache in WP Rocket, browser cache cleared and re-test. I hope this helps someone else.