I realize this is an older thread, but I just started having a similar issue. What I've realized, in my case, that the solver fails both via the CLI and via ekos when there is a parenthesis in the filename or path. Perhaps you all are having a similar issue?
Some logs here:
CLI:
/usr/bin/solve-field -O --no-plots --no-verify --resort --downsample 2 -3 97.9257 -4 4.95925 -5 15 -L 1.07396 -H 1.31261 -u app --config /home/mike/.local/share/kstars/astrometry/astrometry.cfg -W /tmp/solution.wcs '/media/Storage/Astrophotography/Incoming/NGC 2238 (Rosette Nebula)/Light/OIII/NGC 2239_Light_OIII_600_secs_2019-03-22T00-28-26_001.fits'
Reading input file 1 of 1: "/media/Storage/Astrophotography/Incoming/NGC 2238 (Rosette Nebula)/Light/OIII/NGC 2239_Light_OIII_600_secs_2019-03-22T00-28-26_001.fits"...
Extracting sources...
augment-xylist.c:941:augment_xylist Source extraction failed
image2xy-files.c:47:image2xy_files Failed to open FITS input file /media/Storage/Astrophotography/Incoming/NGC 2238 (Rosette Nebula)/Light/OIII/NGC 2239_Light_OIII_600_secs_2019-03-22T00-28-26_001.fits
../util/cfitsutils.h:26:cfitserr could not open the named file
../util/cfitsutils.h:26:cfitserr failed to find or open the following file: (ffopen)
../util/cfitsutils.h:26:cfitserr /media/Storage/Astrophotography/Incoming/NGC 2238 (Rosette Nebula)/Light/OIII/NG
../util/cfitsutils.h:26:cfitserr C 2239_Light_OIII_600_secs_2019-03-22T00-28-26_001.fits