So I have connected this display to my ESP 12F and it was working ,later I decided to reuse the display in another circuit so I did just that. Now when I connect it to my project it does not work, I looked at the back side and there is a voltage regulator 662K which is a 5 v regulator and I test it with my Fluke meter. It shows 5v in and 3.3 v out with respect to ground. Also the D1 diode reads 1.1v and reversed leads show .53v.Connection to ESP is as follows, VCC 5v GND to G , SCL – D1 Gpio5 and SDA-D2 Gpio4.Any help would be appriciated.

Hi Larry.
Try to run a demo sketch for the OLED display and see if it is working.

ESP8266 0.96 inch OLED Display with Arduino IDE

There might be some wires that are not connected properly or some faulty wires.
Regards,
Sara
 

Yes I have tried this and to no avail, it did work but for some reason it just never worked again. Just lost as t why it would just quit, as you can see the values given as far as I know should be correct.

All of these boards and components are very susceptible to static electricity. If you’ve ever felt a jolt when opening a car door or the like, that is in excess of 5,000V (Almost zero current so you don’t die). As these boards/components are designed for a max of 3.3V or 5V you can imagine that static electricity can cause massive damage internally (You won’t see anything wrong). Everyone should always wear an anti-static strap on their wrist, at least connected to the ground of the board (It’s the potential difference that causes the damage so connecting to the board ground can help reduce it)  and, preferably to common ground (Like the ground on a power outlet).
 
Always have a second board on hand. If you think the first board could be damaged, try the second. If both don’t work then check your wiring and/or code.

Hi Larry.
I would suggest the same as Steve. For some reason, your OLED display might be broken or the board.
If you have replacements, it would be easier to find out what might be wrong.
It might also be something related to the wiring.
Regards,
Sara