I'm not going to tell you what to do but I don't think you understand how this forum works. In your case, the DFROBOT library link has a Serial mode and a Parallel mode link. The Serial mode link has several different possible connection methods (in the "test" example program). Telling us "I wired them THAT way" is really not going to get you closer to your objective. You need to take them one at a time and say "I am attempting Serial Mode , method -1. My connections are as follows: etc. Then people can try to talk you through that approach. Saying " I did everything and nothing worked" will get you nowhere fast. You need to pick something and do that, and hope someone responds to that approach. No one is going to want to help you if generalize . If you keep it specific it gives people something to focus on and work with. For example: I posted:
Explanation of exactly what you did to try to get it to work, INCLUDING the POWER CONNECTION DETAIL (ie: what voltage you connected to the display) and wiring detail of how you connected it.
You ignored this and just said "I wired them that way". You could have posted this:
Power Supply: 4.5～5.5V
Display color：blue lit with white char
View angle：170 degree
Control interface：8/4 bits Pallelel (Default) or 3 bits serial (SPI)
and said "I connected it to 5Vdc per above Specs" to let me know that you used the correct voltage, so I can rule out that as an issue. When you are asking for help on the forum, anything you do OR DON'T DO will effect whether people want to deal with your issue. If you appear to be lazy or not detail oriented, people may become discouraged to help you because you are not dotting the "i"s and crossing the "t"s. Your display runs on 5V so we can rule out the possibility that it was damaged by an incorrect ps voltage. That being the case, there is probably nothing wrong with it , ESPECIALLY since you got it from DFROBOT. The reason that is important is that they have a good reputation and they also PROVIDE SUPPORT. You don't know that because you haven't bothered to send them an email. If you had you would have received a reply from a guy named Lie Chu telling you what to do. He helped me and I didn't even buy my display from DFROBOT. There is a 90% chance that your problem is operator error but until you change your approach I don't think you are going to get anywhere. Take notes. Create wiring lists, draw diagrams. Do something if for no other reason than to be able to say you did it and how you did it. I don't know how you expect anyone here to help you when you tell us you tried everything CORRECTLY and nothing worked. The inclination is to be sceptical...