Synthetics canary doesn't pass certificate

We are using canary to try and hit an API endpoint through proxy. The connection requires mTLS therefore we provide a key and and certificate as part of the code. We've captured the traffic and we found out that the length of the certificate is 0, therefore we suspect that canary doesn't pass it through. The canary is based on the Hearbeat monitoring blueprint. I added the following snippet from how-to-validate-authentication-with-self-signed-certificates-in-amazon-cloudwatch-synthetics as instructed and modified a little bit.

        await page.setRequestInterception(true);

        const key = await getSecret(process.env.key);

        const cert = await getSecret(process.env.cert);

        log.info("Injecting request with certificate and key.");

        page.on("request", (interceptedRequest) => {
            const options = {
                method: interceptedRequest.method(),
                headers: interceptedRequest.headers(),
                body: interceptedRequest.postData(),
                cert: cert,
                key: key
            };
            const request = https
                .request(interceptedRequest.url(), options, function (response) {
                    response.on("data", function (data) {
                        interceptedRequest.respond({
                            status: response.statusCode,
                            contentType: response.headers["content-type"],
                            headers: response.headers,
                            body: data,
                        });
                    });
                })
                .on("error", function (err) {
                    console.error("Unable to call %s", options.uri, err);
                    return interceptedRequest.abort("connectionrefused");
                });
            request.end();
        });

The key and certificate are stored in secrets manager and are not empty.