I tried "i need some holiday and a rest" and got it marked wrong because i said "holiday" instead of "holidays" - but no-one says "i need some holidays" in English. "I need some holiday" means i need some time off. "I need some holidays" would mean i need to go away on holiday several times.
In England we rarely use the word vacation. We are much more likely to say holidays - in the plural because this a a contraction of the original “holy days” church festivals when people were granted a day of rest. If I say a holiday, I am just as likely to mean a single day as several. We ask each other “What did you do on your holidays.” Therefore I believe that the plural form, “holidays” should be permitted as a correct answer. To finish this lesson I am going to have to take a vacation instead... not at all English!