There was quite a bit of change so the issue could be anywhere within the opertion. To start troubleshooting lets first look toward your device.
Since the upgrade to lollipop to cover all bases just assume everything reverted to its original state. looking at the basics go to developer settings and verify USB debugging is enabled. next connect device to PC and now within the device verify that MTP is enabled. two ways to check one the devices notification pull down menu press the connected as media device enable media device (MTP). the other option is to go to settings/storage/menu-dots/USB computer connection then verify MTP.
Next focus on the PC next and with changing from 32 to 64. Its thorough to just assume if it changed then compatibilty issues followed. So go to devices and check that the proper drivers are installed.
Device manager click launch emulator and once its up that means its time for adventures in ADB.
check what itt returns and if the question marks are still present then try this.
hopefully by this point you are up and running that was just a few common causes.