Hola Steven

This is because these are test-questions that are testing a specific conjugation of a specific verb. In these tests you will always find a hint telling you which verb and which tense we are testing, in this case "andar" and the preterite. If another verb is used (even if it is a synonym) the system will consider it wrong as it is not what it is asking for. 

I hope it clarifies it.

Saludos cordiales