The Client comes online and goes offline every minute or so

I have a ownCloud server on virtual box using ubuntu 16.04 server. The client is on a laptop ubuntu 16.04 and a lg smart phone. The system worked fine after install. That was 3 or 4 months ago. I it used for about a month then I didn't need it so it was off for a month or so. Now I have a group project and need the owncloud. The phone no longer uploads at all. The lap top comes on line long enough to log on to the server then goes offline.

Please use plain English! I am not a programmer. I need step by step trouble shooting in simple, plain, easy to understand common everyday language. NO TECH JARGON! Please do not assume I know computer speak.

Thank you.

Can you still log on the web interface?

For such errors, it is helpful to get more information from the logfiles: