I had the same problem on the PS4. The last mission that was completed on Hordafulke was A Brother's Keeper. After the mission concluded by logging back into the animus, Evior appeared back on the dock in Ravensthorpe, but no new missions triggered - Hordafulke still showed as unfinished, there were still 2 more order members left for me to assasinate, talking to Randvi resulted in a crash, subsequent attempts didn't start anything, and there were no main-quest markers. Pledging the last remaining territory - Hamtunshire wasn't possible.

Restarting the PS4 and re-loading an earliest possible auto-save triggered a cutscene on the dock of Ravensthorpe properly, resulting in Hordafulke Arc completion message. Pledging of the new territory became possible after a few more cutscenes.

Unable to pledge Eurvicscire after all other lower level content is complete. Only Jorvik , Snotinghamshire and Glowecestrescire are available.