Configure the Google Play API of your app in order to allow IAPHUB to validate your Android receipts.
1. Enable API access on Google Play Console
1.1. Go to the Google Play console and go to Settings > Developer account > API access
1.2. Choose a project to link and agree to the terms and conditions
If you do not already have one, create a new Google Cloud project.
1.3. Click on the link to create a service account
1.4. Click on the link to go to the Google Cloud Platform
2. Configure Google Cloud Platform
2.1. Click on the link to create a service account
2.2. Enter service account name and description and click on the create button
2.3. Select Owner role and click on the done
2.4. Open the actions menu and click on Manage keys
2.5. Click on Add Key and then click on Create new key
2.6. Select JSON and click on Create
2.7. A JSON file should be downloaded, it gives access to the service account, store it securily you'll have to upload it on IAPHUB later
3. Configure API access on Google Play Console
3.1. Go back to the API access page of the Google Play Console, your service account should appear, click on Grant access
3.2. Enable the 3 permissions below and click on Invite user
3.3. A modal should appear, click on Invite user
3.4. You should be redirected to the Users and permissions page, click on your service account
3.5. Click on Add app, select your app and click on Apply
3.6. A modal should appear, click on Apply
4. Configure app on IAPHUB dashboard
4.1. Go to the settings of your app on the IAPHUB dashboard and upload the JSON file you've downloaded previously on step 2.7
5. Wait for changes to take effect
It could take up to 36 hours for the changes to take effect and the Google Play API to work properly, until then IAPHUB won't be able to validate your receipts and you'll receive errors.
But there is a hack that might help you, if you've created your products before creating your service account, update the description of one of your product and click on Save (on the Google Play Console).
It'll force the refresh of your Google Play API credentials and will probably fix your issue.