Hello @sock2me:
Let’s break down what you want to do step-by-step.
1) Display GravityForm form inside a popup.
2) Following form submit (inside the popup), display another page inside a popup.
The use of GravityForms inside a Popup Maker (PUM) popup is well documented. Make sure to refer to the following PUM docs to set up a GF form correctly:
1) https://docs.wppopupmaker.com/article/225-close-popup-and-create-cookie-after-gravity-forms-submission
2) https://docs.wppopupmaker.com/article/377-form-submit-success-options-added-by-popup-maker // See section on GravityForms.
The second step (display a second page inside a popup following form submit) involves rendering ‘remote content’ (RC) into a popup. Let me refer you to a Popup Maker doc on that topic. It’s a simplified approach to rendering RC without the use of the Popup Maker RC plugin extension.
https://docs.wppopupmaker.com/article/370-add-a-single-post-page-or-custom-content-type-to-a-popup
Perhaps the simplest way to display that second popup is to activate the Popup Maker Advanced Targeting Condition premium (paid) plugin extension and use either the Cookie Exists or Cookie Is targeting condition. PUM would detect the cookie set by the GF form submit and then activate a second popup for display. You could use an AutoOpen trigger for the second popup once it’s activated.
See: https://docs.wppopupmaker.com/article/237-advanced-targeting-conditions-cookie-conditions
Popup Maker used to have a demo site you could test all this out on. It appears to be unavailable at the moment. Contact the Support Team at https://wppopupmaker.com/support/ and see if they can help with that.