"Does he meet his family every weekend?"
There are multiple issues with this question.
- The time period can go before or after the subject, but the answer only accepts after.
- The question asks you to translate "meet", which is more accurately 见面, but only accepts the less accurate 见. It should accept both.
- His family can be expressed as 家人 or 他的家人. It only accepts the former.
Most questions on duolingo accept all of these variants, which makes this question even less intuitive - as if you apply a rule you've used in other questions here you might mistakenly think this sentence has some special property that means you cannot say 他的家人, for example.
The only times that do not require measure words are 天 and 年. Every other time requires a measure word (个).
An easy way to remember it is because Day and Year both use 今天/今年 (today/next year) or 明天/明年 (tomorrow/next year) whilst every other time uses 这个 (this) or 下个 (next)