If you’re interested in learning more, I’ll leave a hyperlink to the step-by_explained process for Google Ads enhanced Conversion Activation starting at the beginning.

After you have enabled the enhanced conversion option in Google Ads, it can take up to five days for the Include user provided data from your site checkbox to be added to your GTM Google Ads Conversion Tracking tag. If the feature is not available after five days, you can contact the Google Team for assistance.

After several calls, emails and a month later, the problem was still not solved, I decided to try the old-fashioned method of restarting the computer. Although it isn’t really restarting the computer, it was a similar solution that worked in this case.

How can you fix this problem?

Follow these steps to get started:

1. In the same account, create a new container
2. Click on the Google Ads Conversion Tracking Tag in a New Container and the option click Include user-provided Data from Your Websiteshould appear
3. Import the entire tracking setup from the container you have just used and export it to the container you are using.
4. You can update the GTM ID number in the webshop GTM extension or your Google Tag Manager shortcode depending on how you connected GTM. Then you are ready to go and complete the Enhanced Conversion setup 

It worked in a few cases for our clients, so you might try it, it may work for your case too!

Need help with GTM

We can help you if you are unsure how to configure Google Tag Manager on your store. Let us review your Google Analytics and Google Tag Manager to help you determine if your tracking setup is correct and whether or not the user behavior data is accurate. Prepare a recommendation on optimizing advanced GTM/GA tracking and Enhanced eCommerce setup. Also, consider what additional eCommerce events should you start or stop tracking.

Source https://inchoo.net/online-marketing/manually-enable-enhanced-conversions/