I have the same issue. We are an LTI consumer...Moodle 3.6 to Moodle 3.5 connection....
The error message we receive is:
An error occurred when launching the external tool:Debug error: Expired timestamp, yours 1551448244, ours 1551447910
This has to be an error, updating our server time to match the LTI publisher's server time doesn't make any sense....as it would cause confusion and errors with our learner.
Does anyone have a solution for this issue?