"I wake up at nine o'clock every morning."
I used 毎朝九時におきます and it said it should be 毎日9時におきます
Why 毎日 here instead of 毎朝 ?
Its not required, but adding it wouldn't be wrong, it just might come across a little clunky or unintentional. は does wonders to bring extra special attention to what comes before it. If you did 毎朝は, it means "EVERY morning, ..." providing extra emphasis on the "every morning" portion, whereas 毎朝 on its own is just "oh yeah, by the way, in the mornings, i happen to..." casual.
This rule holds for vague times within Japanese, such as 今日 (きょう - today), 明日 (あした - tomorrow), 今 (いま - now), etc... There's no need for は or に.
If you use an absolute time, a particle is required: 九時 (くじ - 9 o'clock), 四時半 (よじはん - 4:30), etc...
I believe that you can turn an absolute time into a relative time by adding 頃 (ごろ) or 位 (ぐらい/くらい) - 九時ごろ (about 9 o'clock), 九時位 (about 9 o'cock). Once you do this, it no longer requires は or に.
は usually refers to something specific and can be translated with 'as for A, B'. Every day is not a specific day, so it does not need は.
This one is unusually picky about kanji vs kana. Trying to use 起きます or 毎朝 fails, with the latter telling me it should be 毎日.