Why display samples don't show anything when customer side test it?

Few months ago we shared an article about reason why displays don't work when tested, which happen from time to time. Today we'd like to make supplement based on previous article, as below.

One of the main reason is because of the display physical issue, such as destroyed connection side, FPC, bad components, bad IC bonding, bad ITO or broken lcd glass material, etc. So for supplier, they must protect all the material and do the production process in right ways, and many details to be taken care. For example, all the material must be brand-new and grade A, and strictly operate the production line according to the operation guide in workshop.

On the other hand, there is some situations that display are physically all in good conditions, however, the sample doesn't work when customer test it, although sample is working well at supplier side. Except physical problem, the biggest reason is about touch IC firmware. For example, if the lcd display sample is different IC from customer's current display, in this case, display supplier will need the control board of customers to adjust the lcd display's firmware accordingly with IC supplier. That being said, sometimes without customer's control board, supplier is not able to adjust the lcd display to make it work with motherboard. Even sometimes the sample's pinout, driver IC and touch IC are totally the same as customer current display, it could happens that the sample could not work with ctm control board, because the setting IC firmware doesn't match, so will need customer's control board to adjust.