Recently upgraded farm from 2010 to 2016. Still using 2010 workflows, but the migration apparently did not do well for our custom ones. These workflows appear to start up but do not assign tasks to approvers. I've tried to load them in Designer 2013 but it just opens a page saying Designer cannot display the item. There's also the concern that my Visio version being 2016 will cause a problem with it. Should I just scrap all these old workflows and move on to the 2016 workflow platform, or is there a way to fix the 2010 ones?
you'll have to do some things...
First install all the recent updates for SharePoint Designer, there are some bug fixes in the last two sp1 upgrades
have you installed the Infopath service ? workflows 2010 require it as the workflows 2010 contain infopath forms
After that if your sharepoint designer is still displaying errors then i would remove all the cache and stop SP Designer from catching data.
and after that i would stat to check if SP designer is running into compatibility issues, i had one with SP designer and Visual studio 2015, i had to
- Unistall visual studio
- Unistall Sharepoint designer
- install sharepoint designer
- install sharepoint designer SP1 update
- install all sharepoint designer patches
- install visual studio again
after that check if your lists have the correct workflow associations
go to your list in SP designer
go to the list and check the workflows,
if you have missing workflow click on the workflow box and then click at the ribbon button "Associate existing workflows"