-sou + negative past - what is the meaning? e.g. 行けそうで行けなかった場所, 解けそうで解けなかった謎

Question

Still with the Zelda guidebook translation :) I cannot understand the meaning of the third line. It uses ・・・そう・・・なかった. I understand -そう as "seems like" and なかった as past negative, but how do these go together?

Note: My translation tries to stay as close to the original Japanese as possible whilst still making sense. I find it helps me for future reference if I translate the words rather than the meaning (so that's why it comes across as sounding like Master Yoda is speaking).

まずはマップとコンパスを手に入れたい。First of all map and compass you will want to obtain.

それを頼りに、宝箱のある部屋をチェックして回れば、そのダンジョンだけにある特別な　アイテムをゲット出来るはずだ。 Relying on these, if you check the rooms around the treasure chest place [on the map], that dungeon as might be expected special item should be got (collected).

それがあれば、行けそうで行けなかった場所、解けそうで解けなかった謎の多くが解決する。 If you [do] that, a place it looks like you were not able to go to, many mysteries it looked like you could not solve can be resolved (?????????????????????????)

Answer 1

I think ～そうで～ない is a pattern that means "seems like ～ but not ～". Often (but not always) you find the same predicate repeated. So:

行けそうで行けなかった場所
places it seemed like you could go, but you couldn't

解けそうで解けなかった謎
puzzles it seemed like you could solve, but you couldn't

Less literally:

行けそうで行けなかった場所
places you were almost able to get to / places that were just out of reach

解けそうで解けなかった謎
puzzles you were almost able to solve / puzzles that you couldn't quite solve

If you have the map and compass, you'll be able to get to many places you couldn't quite get to and solve many puzzles that you couldn't quite solve. (This is a loose translation.)