cs50 Pong Love2d cant open files

i am doing the cs50 class project on the second folder Pong. trying to open it and all of the following folders all give me error messages. This is among the first

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Error

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push.lua:101: attempt to call field 'getPixelScale' (a nil value)

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Traceback

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push.lua:101: in function 'initValues'

push.lua:48: in function 'setupScreen'

main.lua:47: in function 'load'

[C]: in function 'xpcall'

[C]: in function 'xpcall'