Comment 4 for bug 1642667

-appears to be a duplicate of Bug 1627817

the workaround proposed in
https://bugs.launchpad.net/inkscape/+bug/1627817/comments/2
can also be applied retroactively. In other words, if you have applied the knot LPE previously to a set of circles and if it did not work then you may be able to apply this fix and the LPE will start to work. The svg file will probably remember the fact that you tried to use the LPE and will apply it successfully after you convert the arc elements to Beziers.