You are likely to get this error with paypal if there is something wrong with keys or you didn’t follow the instructions, Make sure you follow instructions in order to prevent such errors.
There maybe a case where live Keys are not working while sandbox keys are working fine or perhaps none of those is working. in order to know the actual cause of the issue and most relevant error you would want to do following.
- Login to root SSH using root credentials. once logged.
- Run following command
curl -v -u "client_id:secret" "https://api.sandbox.paypal.com/v1/oauth2/token" -X POST -d "response_type=token&grant_type=client_credentials"
Please make sure you replace client_id with your Client ID and Secret ID with your secret ID. then hit enter once execution of command completes you should see actual error in the terminal.