Solution I found after searching and testing many things. I saw a video on fixing steam games that don't launch and it suggested moving the game to a faster drive. I moved Spiral Knights to my "E:" external drive and it is able to launch again. My C: drive in which the game was previously is an SSD (propably older than E:), it had ~50gb of free space and ran the game yesterday. I don't know what went wrong... 😅
The same problem occurred again seemingly out of nowhere and after reading the launcher log I checked the "run as administrator" option (properties/compatibility) for "java.exe" and "javaw.exe" in the game files.
Solution I found after searching and testing many things. I saw a video on fixing steam games that don't launch and it suggested moving the game to a faster drive. I moved Spiral Knights to my "E:" external drive and it is able to launch again. My C: drive in which the game was previously is an SSD (propably older than E:), it had ~50gb of free space and ran the game yesterday. I don't know what went wrong... 😅