question

I have a skill that works fine when tested through Alexa Simulator. The logs on CloudWatch also are as expected.

However, when I test on a real device, the skill just ends the session and I see the following in my CloudWatch logs.

It says Alexa encountered an internal error. What could it be?

SkillId: amzn1.ask.skill.916edbcf-e7fd-4d8e-be91-bb3da117e526

{
    "version": "1.0",
    "session": {
        "new": false,
        "sessionId": "amzn1.echo-api.session.ae52c489-9a8f-49b2-909c-df9f3959ac79",
        "application": {
            "applicationId": "amzn1.ask.skill.916edbcf-e7fd-4d8e-be91-bb3da117e526"
        },
        "attributes": {
            "isDeductible": true,
            "isAlexaIntegrated": false,
            "categoryId": "3"
        },
        "user": {
            "userId": "amzn1.ask.account..."
        }
    },
    "context": {
        "System": {
            "application": {
                "applicationId": "amzn1.ask.skill.916edbcf-e7fd-4d8e-be91-bb3da117e526"
            },
            "user": {
                "userId": "amzn1.ask.account.AGST5AJ2NS3AM4PTRWYEEWCFWRZ36NFHMHF46ED7WAQZXGXHEWQCHG6KGVKC4GUB5HRE6C7UA36CSTWKUGUJ3VE6BMBVFKQIXIJPWUWTBEEBMBZ4VYS5NMC7L7FMKECWTXNXHSB3SRRWHZ6OHGFZ44GRPE6LRTYJMLQU2COK76O33DLHR4NP3HKIY3BWEMFS7JBI3WP7VVAZ5GI"
            },
            "device": {
                "deviceId": "amzn1.ask.device.AF4JZD2EE75CHDOM4Q3HWPJGNZWAVMPWTE2H2X2TCYEWUSAGM7TKCTE2JFT4AG5FXONYPYQ4YNNIJXRGAFFPL5HVYELXERCF5M2KG7Y6DIJRIAQN2LRHWDGMDMKLG2PJA32NRBC7YJ2X6SEWP5JC2MSIUY4S5YOLSSV2JIQKEL2LQMECBMPUY",
                "supportedInterfaces": {}
            },
            "apiEndpoint": "https://api.amazonalexa.com",
            "apiAccessToken": "eyJ0eXAiO..."
        }
    },
    "request": {
        "type": "SessionEndedRequest",
        "requestId": "amzn1.echo-api.request.95ddc9ba-4e71-4d11-bb6f-9b87c9570e5a",
        "timestamp": "2020-09-11T20:48:10Z",
        "locale": "en-US",
        "reason": "ERROR",
        "error": {
            "type": "INTERNAL_SERVICE_ERROR",
            "message": "Internal Server Error"
        }
    }
}