rew not accepting old umik 1 calibration files

[pjwd]

apologies for a possibly dumb question but I have an old umik 1 that has two txt caliibration files . REW see umik but when I add either of the files it shows a red cross - is this because it is too old
there also appears to be only L and R inputs to add 2 txt files 9 also a red cross)

thanks
Phil