Firstly check that you are using your correct ECB username and password - the easiest way to do this is to login to the Play-Cricket website.
We have seen occasional problems related to the ECB SSO login system whereby you are using the correct username and password but still get a 401 error. The way to fix this is to change your Play-Cricket password and try again.

Never.
We use your credentials to validate your use of the P-C API on a per session basis, your credentials are never stored by us, the only storage of credentials is in the form of a cookie on your local machine if you select the 'Remember Me' option.

A fixture file contains details of a future match. It assumes that no toss has taken place and the players may not have been selected
If players from one or both teams have not been selected on Play-Cricket then you have the option of downloading the entire player list from that club which you can load into TCS during the fixture import.
A match file assumes that the match is in progress and will contain data relating to the current state of the match.
In general you will want to create a fixture file.

If you set the match result to be in progress during a file upload this indicates to Play-Cricket that you are submitting a 'live score'.
The current state of the match will be displayed on Play-Cricket, since this is a manual process at present you may want to do it after every 4 overs or at intervals.

NB. Do not use this option for league matches until the match is actually in play, in other words don't test using a league fixture. This locks the match on Play-Cricket and only a league administrator can unlock it.