Hi, 

I am running Magento version 2 on Ubuntu 16.04.2 LTS running PHP 7 FPM. 
Magento was throwing an error - invalid user ID. 

I'm looking at the logs for errors and am not finding anything that
looks like what I am looking for. 

The site is full time SSL. 

The SSL vhost is configured "ErrorLog /var/log/apache2/ssl_error_log". 

Is there some other place I should be looking? 

Thanks in advance for your help!! 

Keith