All HTTPS API are case-sensitive. Request path and query parameters letter-case shouldn't be changed.
Make sure you're using the correct server. Blynk currently have 2 clouds running.
The old cloud (no longer supported) with host
blynk-cloud.com and the new cloud with host
In case you're getting the
Invalid token. response from the HTTPS API,
and you're sure the device auth token is correct - it could be a GEO DNS issue.