Maybe useful for someone or not.
Anyway, I made this, and it seems to me useful to know.

Front display error status, three cases,
1 What happens without a sim card.
2 What happens if the sim card is wrong or damaged.
3 What happens if a wrong image file is uploaded.

1 & 2 can be a faulty sim card, the third is to solve.

(Thank you to Toysoft for publishing it)

All the best about hardware/support from Johnny_B, link :
http://jb8a8f8.com
http://jb8a8f8.nl