hoeui junge keompyuteoga gapjagi kkeojyeo beoryeoseo bogoseoreul mos bonaesseoyo.

회의 중에 means during the meeting / in the middle of the meeting.

• 중 = in the middle of / during (a time or activity)
• 중에 is commonly used when you mean at some point within that time (often when something happens unexpectedly during it).
  You’ll also see 회의 중 without 에; it’s similar and often interchangeable in casual speech, but 중에 can feel a bit more like while (it was going on).

Because this is a time/occasion meaning (during), so 에 is the natural particle.

• -에서 typically marks a location where an action happens (e.g., 회의실에서 발표했어요 = I presented in the meeting room).
  Here, the focus isn’t the physical place; it’s the time context during the meeting.

가 marks the computer as the subject of what happened: the computer is what turned off.

• 컴퓨터가 꺼졌다 = The computer turned off.
  If you used 는 (컴퓨터는), it would sound more like a topic contrast (e.g., As for the computer, it turned off (unlike something else)), which isn’t necessary here.

-아/어 버리다 adds a feeling like (it) ended up… / unfortunately… / completely… / unexpectedly….
So 꺼져 버렸어요 is stronger than 꺼졌어요 and often implies the speaker is annoyed, regretful, or that it happened unintentionally:

• 컴퓨터가 꺼졌어요 = The computer turned off. (neutral)
• 컴퓨터가 꺼져 버렸어요 = The computer ended up turning off / turned off on me. (more emotional/negative)

버려서 is 버리다 + -어서 (because/so), connecting cause → result:

• 컴퓨터가 꺼져 버려서 = Because the computer ended up turning off / since it shut off (unexpectedly)
  Then the result follows: 보고서를 못 보냈어요.

-아/어서 links two clauses and often means because/so, especially when the first clause explains the reason for the second:

• (reason) 꺼져 버려서 (result) 못 보냈어요
  Depending on context, -아/어서 can also feel like and then, but here it clearly gives the reason the report couldn’t be sent.

못 보냈어요 means couldn’t send (it) due to inability/circumstances.
It’s different from intentionally not sending:

• 못 보냈어요 = I couldn’t send it. (something prevented it)
• 안 보냈어요 = I didn’t send it. (choice/decision)

못 is an adverb meaning cannot, and it’s normally written separately from the verb:

• 못 + 보내다 → 못 보냈어요
  The same applies to many adverbs: 잘 했어요, 빨리 갔어요, etc.

보고서를 uses the object particle (을/를) because the report is what you send/submit.
You can omit it if it’s obvious from context:

• 보고서를 못 보냈어요 (clear and complete)
• 못 보냈어요 (natural if everyone knows you mean the report)

-었어요 is the polite past ending in the informal-polite style (often called 해요체).

• 못 보냈어요 = I couldn’t send (it).
  For a more formal setting (e.g., to a boss/client), you might say:
• 못 보냈습니다 (more formal)

Korean word order is flexible as long as particles/grammar make roles clear. 갑자기 can appear in different positions:

• 회의 중에 컴퓨터가 갑자기 꺼져 버려서… (very natural)
• 회의 중에 갑자기 컴퓨터가 꺼져 버려서… (also natural)
  Subjects/objects can also be dropped if understood:
• 회의 중에 갑자기 꺼져 버려서 못 보냈어요. (if it’s clear it’s the computer and the report)