Breakdown of Регистрация закончена, но ваш кондиционер почему-то не включён.
не
not
ваш
your [formal/plural]
но
but
почему-то
for some reason
Questions & Answers about Регистрация закончена, но ваш кондиционер почему-то не включён.
Why do we use the short forms закончена and включён here instead of their long forms?
In Russian, when a past passive participle is the main action or state happening to the subject (like "is finished" or "is turned on"), you must use the short form. Long forms like законченная or включённый act like normal adjectives placed right next to a noun (like "the finished check-in").
How do the endings of закончена and включён work?
Short-form participles change to match the gender and number of the noun they describe. закончена has the feminine -а ending because it refers to the feminine noun регистрация. включён has no ending (a zero ending) because it refers to the masculine noun кондиционер.
Where does the -ён in включён come from?
The verb включить (to turn on) forms its participle with the suffix -ен. However, in the masculine short form, the stress falls on the last syllable, which changes the е to ё. It is important to remember to stress this final syllable when speaking.
Could I use почему-нибудь instead of почему-то for "for some reason"?
No, you need почему-то here. We add the -то suffix to question words when a fact is real or already happened, but we just don't know the specifics (the air conditioner is off for a specific, but unknown reason). The -нибудь suffix is for hypothetical, future, or "any at all" situations, which doesn't fit this real, current state.