In order to use properly McTime's API please consider the following restrictions:
There's a rate limit of 10 requests per second. If you get over the limit, you'll get the error "Too many requests" (Code 429).
If no connection within 60 seconds can be established, you'll get the error "Connection time out" (Code 503). Try to connect in such a case again.
If no response cannot be formed or calculated within 60 seconds, you'll get the error "Read timed out" (Code 504).
Try in this case to reduce the amount of requested data by reducing for example the date range or the amount of queried users, organizations, time entries etc.