I have a few 860c displays and they always worked fine. They were my favorite for awhile as they are plainly visible in bright sunlight, and have an internal setting that will let you see both realtime watt and amp output, simultaneously.
If its saying 'welcome' and blacking out, thats almost certainly a bad display. I would return it asap so you can get another display in hand and ensure its not something else worse like the controller that is winking out on you.
I said the 860c was my favorite for awhile... I went to minimalist displays a little over a year ago and you can get hold of a DZ40 for under US$30 on AliExpress. That would not be a terrible cross-check to get your hands on to try out. I just had another one delivered to me to replace another 860c. While I was at it I bought an inexpensive 1T4 wiring harness for the sake of having a backup... which is another thing you can use to ensure the problem is not a bad pin in your display line.
Amazon sells DZ40's for about double the Ali price but fast delivery.