Help regarding ASAT 11th to 12th moving

so we had our ASAT in i guess december which was for the discounted price, i gave the exam and got if 25% but I didn't buy the course at that time and now I'm planning to give ASAT again but idk the date man. it was on 1st March but due to my finals I couldn't give. now on registration it's showing no test slots available. when can I give and is it possible to use the 25% i got in December? please help.