Mailed my return, it's been over 6 weeks and still not processed, should I be concerned that they didn't receive it?

[Bsch4477]

Look here. 
https://www.irs.gov/wheres-my-refund

[Mike9241]

6 weeks is not that long for a mailed return. in the future i suggest if you are going to mail your return you use a tracking service so you know the IRS got it. also use tracking for state return if that applies 

[xmasbaby0]

It could take at least four weeks for a human to open the envelope and enter your return into the system.   Once it is entered, you should be able to see information on the IRS refund site.  

Your ONLY source of information about your refund now is the IRS.

You need your filing status, your Social Security number and the exact amount  (line 35a of your 2023 Form 1040) of your federal refund to track your Federal refund:   

https://www.irs.gov/refunds