I mailed my federal return the end of January and haven’t received anything from them. Should I mail another copy to them?

That's typically not advisable if they have already received it. Were you expecting a refund? If so you can check your status with the IRS on Where’s My Refund? it has the most up to date information available about your refund. This will confirm the IRS did receive your tax return. If you were not expecting a tax refund you can contact the IRS to see if they received it. 

You may contact the IRS at 1-800-829-1040 please see this website article from the IRS on contact hours and information you will need to have ready when calling them: https://www.irs.gov/help/telephone-assistance.

Here are some tips when contacting the IRS:

• First choose your language. 
• Then do not choose the first choice regarding REFUND, or it will send you to an automated phone line.
• Instead, press 2 for personal income tax questions.
• Then press 1 for form, tax history, or payment.  
• Then press 3 for all other questions.
• Then press 2 for all other questions to be transferred to an agent

Please see this TurboTax FAQ on what to have ready before you contact the IRS: https://ttlc.intuit.com/community/irs/help/what-do-i-need-if-i-call-the-irs/00/27378