Record responses from Form to SharePoint List & Apply Auto-Increment number

Hello

I have spent a couple of days trawling through other conversations that are related to my query, but I can't find the answer I'm looking for.

I have a decent amount of experience with SharePoint and have set up some simple flows but this is the first time I've attempted something complicated and I'm hoping there's a simple solution that I'm just not seeing...

I have a SharePoint List set up called "Improvement Register" that is used to manage improvements as part of our quality system. Suggested Improvements are submitted via a simple Form.

Initially, I set up an automated Flow to record responses from the Form to the List, which worked fine.

This is the Flow for reference:

Last step is an email notification to the management team that the item has been created.

In addition to this, each item (i.e. Suggestion) needs to be allocated a unique ID in the form of "IMPXXXX". I followed the instructions provided by RobElliott  in this post: https://techcommunity.microsoft.com/t5/sharepoint/auto-increment-number-field-in-a-sharepoint-list/m-p/1141477/thread-id/37988 to set up the auto-increment number. This flow works fine when I add an item directly into the List via SharePoint. But, when an item is added through the Form, this flow doesn't work. 

I'm sure I'm missing a simple step to connect the two but I'm just not experienced enough with Flow to see it. Any assistance anyone can offer would be greatly appreciated!

Cheers

Kerry