Hi @Raman,
Does the Host header coming in to tyk contain tyk.heatmap.visitor.analytics.abl-solutions.io? If that is the address that hits nginx it seems possible it will not be the address that nginx sends upstream to tyk.
The API is configured with "domain": "tyk.heatmap.visitor-analytics.abl-solutions.io" so it will be looking at the Host header and if that doesn’t match it will not identify that this is the API to be called. Which will result in a 404
If you have no other APIs defined in tyk you could try removing the domain config from the API to verify this.
Cheers,
Pete