The files changing to .ERR could be a problem if your computer has Windows 10. Try Windows 7.
Go here <LINK_TEXT text=“viewtopic.php?f=22&t=4823&start=80#p28237”>https://forum.seeedstudio.com/viewtopic.php?f=22&t=4823&start=80#p28237</LINK_TEXT> and try to load the LIB code from the zip. See if says .RDY for you. After that it will say No APP Found on the screen. This is step one.
Helpful info http://wiki.seeedstudio.com/DSO_Nano_v3/