Hi and welcome to the forum
Hope neemo's suggestion does the trick. If it doesn't read this:
Not sure what tool you used to re-combine the 2 partitions into 1 large one; but, in W10 you can't access a single drive partition larger than 2TB using
MBR disk format. So, if you didn't originally format your 3TB hard drive (both partitions) using the
GPT disk format, that is problably your problem. You must have your hard drive formatted to
GPT format in order to access a single partition larger than 2TB, which your 3TB certainly is.
Suggest you backup your exiting files on both partitions to other external media, such as a different >3TB hard drive or a Cloud drive such as Microsoft OneDrive or Google SkyDrive. Then use a program such as Partition Magic or ISO-Linux GSmartControl (free from UBCD.com) to reformat your 3GB hard drive. Do
NOT use an image backup program to backup your files such as Macrium or Acronis, rather use a folder-by-folder backup program such as the free AOEMI Backupper to do this. Restore your files/folders back to the newly GPT formatted 3TB drive with the single partition. Once done, W10 should allow you to delete those Quick Access shortcut links.
Let us know how it turns out,
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