A user with a similar problem found that his paper wallet's private key was in compressed format, and needed to be in uncompressed format before electrum would accept it.
An offline copy of this website can convert a private key to uncompressed format.
https://www.bitaddress.org/These quotes show the user's problem, and the solution.
When I select
wallet>private keys>sweep
Window opens & I paste private key from paper wallet - but the "sweep" button does not highlight, stays inactive. Assumed private key was incorrect, but I tried four different ones, several times, and still nothing. Has this function been removed from this version?
If so, how to?
You are so right, thank you for the link. The Private Key needed to be uncompressed, and in fact Electrum recognized it...