Well I can understand why I can't play my mono files with the ks plugin there's no way to send a mono signal over spdif correct? but I just converted them to stereo wav from mono flac with dbpoweramp and then I converted them back to flac but I'm still getting an error message

Unrecoverable playback error: KS output error: error opening device

any help I'm sure the answer's probably obvious?
foobar lists channels as stereo now on the new files

thanks for your help

oops I guess the files were 22khz thats why they didnt work...
ok so I converted them to 44.1khz stereo wav
and then to flac

are the files still lossless if the source was lossless? or no?
files are almost twice as big as they were... I'm confused

Yes they are. Before the compression, they are exactly twice as big because now your file has 2 exactly the same channels.
But there's no need to convert them if you use foobar2000. You can use the DSP plugin „Convert mono to stereo”, and it will be done „on-the-fly”.