I guess that should be an I2C issue. I used one OLED as slave before and it works well. Some problems I met are FYI.
When PSoC4 configured as I2C master, must use external I2C pull-ups.
Use another I2C master tool to check if the OLED I2C slave can be emulated and check if it can be programmed.
Are there any hardware connection issue for OLED circuits? When I developed the code, the module I bought from internet can work well, but my PCB soldered by myself can not work... Then I found there was a hardware problem on my PCB...