reply to u/Ag_2402 at https://reddit.com/r/typewriters/comments/1nwl0jb/brother_charger_11/

Remove the ribbon and compare what's happening bilaterally. Use the mirror symmetry of the two sides and the ribbon reverse functionality to puzzle out what's wrong. Is something stuck? Broken? Bent? Missing? Comparing the broken side to the working side should help to solve the puzzle.

Look closely at the mechanics of what's going on. Are the gears turning at all? Is there a pawl that holds the forward motion properly? Does something need to be bent back into place? Is there a missing spring perhaps?

Beyond this doing searches for ribbon advancement on YouTube (especially Phoenix Typewriter's channel) may unearth some illustrative help.

Some of the advice here may be helpful: https://typewriterdatabase.com/RD-Typewriter-Tips.index.manual