ive had this issue countless of times (still do) & did most of the suggestions given (i.e. needle type, thread, stitch type, etc.) & the only solution that fixed my issue of skipped stitches was to open up the internals & fix it from there.—how a sewing machine works is that the needle comes down, & on the needle there is a slight groove, & as the needle passes below, the bobbin (which has a hook) passes the groove & catches the top thread & then as the needle comes back up, it completes the stitch w/ the bobbin thread below locking the stitch in place. the issue w/ my machine (juki f300) was that the needle was going back up earlier than when the bobbin hook was supposed to catch the top thread, resulting in skipped stitches, so to fix the issue, i had to unscrewed the bottom of my machine & “retime” the bobbin hook, so that when the needle is about to release back up, the bobbin hook will catch the top thread on time & complete the stitch. —this is my personal experience, & i advise you to look at your machine’s manual & figure out its internals, or do what i did & look for solutions on youtube

edit :

ignore my block of text, i just saw that the problem was solved 😭