I understood like Single Player loads instead of SA-MP;
If it's that:
Single player can load for 2 reasons - you have installed SA:MP to the wrong folder or you have the wrong version of San Andreas. If you have the wrong version it's easy to fix. .
Click here to download the downgrade patch.
Or sometimes the single-player menu will be shown, but SA:MP will have in fact loaded properly. To fix this you simply need to select an item on the menu then press esc until you're out of it, then SA:MP will proceed to load.