Friend of mine queried last summer, got multiple offers by October/November. Signed with agent awesome (great sales record - powerhouse in the category/genre) in December. After signing, communication was virtually non existent (3-4 emails total in six months). Author didn't mind. Figured it was just how this agent functions. After two rounds of edits with pretty limited editorial notes, agent says it might be best to step aside without much explanation at all.
Now that recently signed
debut* author is again agentless with a book that never went on sub,
1) would protocol dictate that it's okay to reach back out to agents b or c who offered but weren't selected explaining the situation?
2) can author re-query or reach out to those who had partials/fulls who were interrupted by competing agents offer for rep and passed. Or
3) is author pretty much stuck writing a new debut and starting from square one (write new book, query, etc)?
Your friend (who is NOT a *debut author because the book hasn't been sold, let alone published) missed one key element of the signing process: ask the agent offering representation how much work s/he thinks the novel needs before it can go on submission. It sounds like your pal thought s/he would sign with agent, and the ms would go on submision fairly soon thereafter.
This is almost never the case. I can think of only one author I sent out without revisions (Patrick Lee). Everyone else had at least some typos to fix and probably more than half had some major revisions.
My guess here is that your friend did not nail the revisions the agent was looking for. This happens more than any of us would like. It's actually one of the reasons I often ask for revisions BEFORE I sign someone. If they can't revise, it's a huge red flag. Editors will ask for revisions too. I can think of only a couple books that didn't have multiple-page editorial letters before the book was sent into production.
But back to your question: if the book has not been sent to editors, it's fine to query again. Your friend needs the "my former agent I parted ways amicably, before this was sent on submission" probably near the top of the letter for those agents being requeried.
Your friend should be prepared to talk about why s/he parted ways with the agent. When I see that in a query, I do not assume the agent is a dunderhead.