What is the actual model of the accelerator? The Apollo was available in 4 models. The Mk1, Mk2, Mk3 and LC. The full name should be printed on the board under the ram socket.

The Mk models should all accept up to 32MB of ram, or 64 with the optional second simm socket fitted. The LC model will only accept up to 8MB and isn't compatible with the PCMCIA slot.

The only thing that might be a problem is the SIMMs you are using. Are they single or double sided? (ram chips on both sides of the simm) Some accelerator card would only work with one of these types.