I suggest not putting the version of Twine and the story format within the title of your question as it just makes it longer without any real benefit, just using the question tags to supply that information is more beneficial.
You need to fully state each individual expression of a compound expression.
<<if $gameDay == 1 or $gameDay == 2 or $gameDay == 6 or $gameDay == 7>>
<<set $workAlert = true>>
<<else>>
<<set $workAlert = false>>
<</if>>
... you could also use a Array literal and the <Array>.includes() function to achieve the same result.
<<if [1,2,6,7].includes($gameDay)>>
<<set $workAlert = true>>
<<else>>
<<set $workAlert = false>>
<</if>>
You may want to use the keyword operators ("to", "eq", "is") instead of the mathematical operators ("=", "==", "===") as it is very easy to use the wrong number of equals signs.