Ok, there’s a TV series called Blackout (Blackout (2021) - TheTVDB.com) and I tried to add it to my library. But even the curly bracket workaround does not help. Here’s my directory:
user@desktop:~/Videos/Series$ tree Blackout*
Blackout (2021) {tvdb-406231}
└── Season 01
├── Blackout (2021) - S01E01 - Dunkelheit.mkv
├── Blackout (2021) - S01E02 - In der Höhle des Löwen German.mkv
├── Blackout (2021) - S01E03 - Chaos.mkv
├── Blackout (2021) - S01E04 - Ins Herz der Finsternis.mkv
├── Blackout (2021) - S01E05 - Abgrund.mkv
└── Blackout (2021) - S01E06 - Licht.mkv
All other TV series (not shown) do work perfectly.
Naming scheme looks correct, I would check and see if you have any duplicates, if a series gets incorrectly matched as a series you already have in your library, it will seem at first that it just didn’t get picked up at all.