Garmin API fix

I need an experienced API specialist to receive exercise data over my APP. We were receiving data, but showing connected but not uploading data over APP. Should be a simple solution as it was once working. Also, like to upgrade our heart rate extraction from METS to Garmin's new Light, Moderate, and Vigorous identifiers (via their phone APP) that wasn't available before. My backend is written in MYSQL and PHP. Frontend written with reactJS and PHP. Before I award project I need confirmation from developer that they have the skillset to repair this. All repairs are the company's intellectual property.