Hi Robin2.
This time the "Huge White empty area" to type my reply or answer just appeared straight away. So this problem is solved or "SELF FIXED" somehow.
Thanks for the download link you sent. It's the only (Arduio .cc) site I have used for downloads.
This new download is the same 64 bit IDE that I had already downloaded previously.
I found a hidden library in my home folder that was corrupted (NOW DELETED) so library problem is SOLVED!
Last problem NOT solved--- Linux 64 or 32 bit IDE have NO Serial plotter in the "drop down" tools menu ?
I am trying to use a gyro movement sensor and the PLOTTER is helpful compared to the fast numbers in the "MONITOR"
Also trying to PLOT some electrical voltage changes to a GRAPH.
Is this SERIAL PLOTTER a separate download? Or am I missing something?
From your input and help (+ hours of reading) I am slowly managing to be able to JUST get some things almost usable with Arduino.
Thanks to Robin2 and everyone else that has the patience with newbies like me. Once I establish a good ground up foundation! Hopefully I can help others here in future. (Well that's my aim anyway)
Keep a mask on and stay safe. John.