Logs not displaying in Heroku

[rynop]

For example, when /capture_payment produces a 402 the puts call in log_info does not produce an entry in the Heroku logs.

I tried to add a config.ru with the following contents (per this SO) but that did not work.

Here was my steps:

heroku git:clone -a ns-stripe-payment-intent
git clone [email protected]:stripe/example-ios-backend.git
cd example-ios-backend/ && cp -r * ../../ns-stripe-payment-intent/
cd ns-stripe-payment-intent
echo '$stdout.sync = true' > config.ru
git add . && git commit -am 'logging' && git push heroku master

Any ideas? I'm getting the following error when calling /capture_payment from physical android device and trying to figure out why (works on android emulator, ios physical, ios emulator).

Error: The Source src_XXX does not belong to the Customer you supplied cus_YYY. Please use this Source with the Customer that it belongs to instead