Th key here is having only one legend positioned at the top left. To include everything in the legend, remove the NOAUTOLEGEND option and just have one KEY:EGEND statement to telling it move to the top left. If you want only the SERIES plots in the legend, you should do as @FreelanceReinh mentioned and use the NAME option on the SERIES plots and list the names on the KEYLEGEND statement.
It's also important to note that a KEYLEGEND statement with no names listed is how you normally control the AUTOLEGEND, but that legend was disabled by the NOAUTOLEGEND option. Normally, the position of a KEYLEGEND statement does not matter, but I'm thinking that a "positional" AUTOLEGEND was created due to these mix of options. As a rule, use "no name" KEYLEGEND statements for only AUTOLEGENDS; otherwise, names should be specified.
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