Why won't my Nexus 7 2013 screen turn on?

[667Sam]

My Nexus 7 (2013) screen and charging port have both been replaced professionally. Following the charging port repair, the tablet worked at the store, but later the next day when I went to turn it on, the screen didn't turn on. I thought it was just dead so I put it on the charger. I went to check it the next morning and it still didn't turn on. I've tried all of the reset solutions I could find and the most I've been able to do is get the power/system light to blink five times. It will also occasionally produce notification sounds from various apps and my Google Play account shows that is has recently been online - I just can't see anything! Any ideas on what I should do to further troubleshoot this?