If I qualified for student tax credit last year, why do I not this year. I still live at home, and I still work part time. These things were also true last year.

Which credit are you referring to? There is the American Opportunity Credit or the Lifetime  Learning Credit?

To be eligible for AOTC, the student must: 

• Be pursuing a degree or other recognized education credential 
• Be enrolled at least half time for at least one academic period* beginning in the tax year 
• Not have finished the first four years of higher education at the beginning of the tax year 
• Not have claimed the AOTC or the former Hope credit for more than four tax years 
• Not have a felony drug conviction at the end of the tax year 

*Academic Period can be semesters, trimesters, quarters or any other period of study such as a summer school session. The schools determine the academic periods. For schools that use clock or credit hours and do not have academic terms, the payment period may be treated as an academic period. 

More information can be found here: 

Education Credits 

American Opportunity Credit