Which specific version of the 3050?  Always include that on any initial problem post.  e.g. Small Form Factor, Tower or Micro. 

The Tower has a "universal" audio jack.  It doesn't detail whether this is a standard "TRS" jack that will detect either a mic (what I suspect you have) or headset or if it is a "TRRS" jack like is used in iPhones.  

I have optiplex 3050 micro vesa mounted with windows 10 pro

does not recognize headset with mic Logitech h111 single jack. Troubleshooter says no microphone connected. Can hear sound. 

TRRS REQUIRES a splitter.

https://www.amazon.com/CableCreation-Splitter-Headphone-3-5mm-Audio-Jack-CTIA-OMTP-Adapter/dp/B06Y433C3S

I too am having this issue. I have an Optiplex 3050 SFF. and I am trying to get headphones (Panicky PA209) with a mic to work. The jack on the front is a combo mic/headphone. and there is no other jacks on the machine to plug a spliter (which I do have) into. 

I have the same problem with Optiplex 3050, 3060, 3070. 

I have earphone with mic with p3, that works well in my laptop, but in the Dell they don't work, I don't know what to do... I already installed all drivers that have to download in Dell website, but I think that is a driver problem, i didn't find the right drivers to correct this problem yet, but i am sure that the audio drivers that they put in dell website isn't the correct or funcional one.

Anyone got the solution for this?

There are two different "combo" jack applications.  There is one type of combo jack that can be either a headset or mic but not both at the same time.  This type uses a standard TRS plug.  The second type of combo jack will support both a headset and mic at the same time and requires a TRRS plug.

I don't know what type of "combo" jack is in this model.  The Dell documentation I can find doesn't detail this.

The Dell supplied Realtek Sound driver must be used.  

I have formated again using Windows 10 2004 build and didn't install any driver from the Dell website. The Windows Update itself downloaded the correct drivers and now the mic is working. Try that if anyone have this problem. I hope this works in Optiplex 3020 3010 and 3070 too.

@Digox​ I was wondering do you still have this problem? As the 2004 build is no longer supported I am stuck and don't know what to do.

it has a port that can use either trs or trrs