There could be number of reasons why your Lead Ads are not making to your gohighlevel account. Are you an admin of the Facebook page - How to add an admin to my Business Manager

Can you confirm that the correct FB Lead Ad form is the one selected in your Facebook ads manager and matches the one in your Sub-Account? -

https://web.facebook.com/business/tools/ads-manager

Now in your Sub-Account check in settings> integrations > facebook form fields mapping if there is a blue tick mark next to the form you have selected in ads manager.

If you are in fact the FB Admin, can you try this to confirm if Lead Connector is accessible and can allow access to your page?

Once you have completed the steps in the video above, please use the Facebook leads ads testing tool to see if leads are now being added to your Sub-Account.

Facebook Lead Ad Debugging:

Lead Ad Testing Tool:

https://developers.facebook.com/tools/lead-ads-testing

If you see that LeadConnector access to your page has been revoked or the App ID not coming up, you will manually need to assign lead access permissions to LeadConnector on Facebook:

i. Go to Business Suite.

ii. If you don't have access to Business Suite, go to Business Settings and select your business, skip to step (v)

iii. Click the dropdown in the top-left corner and choose your business account.

iv. Click Settings in the bottom-left corner.

v. Click More Business Settings.

vi. Click Integrations in the left menu, then click Leads Access.

vii. Click Assign CRMs. You’ll see a list of CRM systems that have been integrated with your Facebook Page.

viii. Check the circle next to LeadConnector then click Assign.