If your OLED display does not work in Proteus, then simplify things.
Make a new project (or copy the clock project) and remove all clock related stuff.
Start by printing a line of text on the display, or even a single pixel.
If you can draw a pixel, then you know that the simulator works, the schematic in the simulator works, and a whole bunch of other stuff on some low hardware like levels.
Once you have a working foundation start addding more complicated stuff.