Who can I contact I have not gotten a 2nd or 3rd stimulus check?

If you did not receive the first or second stimulus payments then you can use the Recovery Rebate Credit on the 2020 federal tax return.

After completing the federal section of the program, when in Federal Review the program will ask about stimulus payments received.

https://www.irs.gov/coronavirus/get-my-payment

This link will give you the information you need. You can track your stimulus and/or request your credit if you have not received. They had a lot of problems with people accidentally throwing their stimulus cards away since it came in an plain envelope and appeared to be spam. They have had people never receive them as well. Through this link, you should also be able to input bank information if you are looking for a direct deposit if your stimulus has been lost. I hope this helps.