Permission error while upgrading 4.6.0 to 4.7.1

[rob209]

Server configuration has not changed (I am admin) and password is stored in browser, so no error there.
There is only a red box with "bad server response" at the top
How can I debug this error?
After click on login there is a request to /api/v1/App/user which results in 0 bytes response

[tanya]

Run rebuild.php from {your_espocrm_dir}
Check espocrm logs ({your_espo_dir}/data/logs)

[rob209]

I ran "php rebuild.php" from CLI and the output was

[2017-06-06 13:41:43] Espo.DEBUG: Schema\Converter - Start: building schema [] []
[2017-06-06 13:41:43] Espo.DEBUG: Schema\Converter - End: building schema [] []

It is now possible to login again