You just got the rights back from a publisher for whatever reason. Could be they went of business (happening with more frequency) Or the terms of your contract could be up. Always check the terms of rights reversal before you even sign on the dotted line. If after 3 or more years and the contract is up, you may want to consider having the rights reversed to you. In this opinion piece, I am talking about digital books only.
Why keep it with the publisher if it is not selling and they are doing nothing to promote it? (which after the first week or two of release, most publishers don't, unless your book goes viral, then you are their new best friend!) Here's some flowers! We love you until your next book flops! Remember a publisher is a business, not your family or your BFF. Keep your relationship professional.
Now that the book is back in your hands, you have to decide what to do with it. A few pubs will take previously published works with caveats, like you have to be an in-house author or must change the title. Check with submission guidelines before considering resubmitting somewhere. Be prepared, though. A lot of publishers want nothing to do with previously published stories. After having your story lost in a dark wasteland for 3 years or more, why put it back in bondage with another owner?
You might consider self-publishing.
Besides, my writing style and quality has changed so much since that first-ever release. For the better, natch. *wink* I wanted to take my time, reacquaint myself with the plot and characters and time travel in general. At 23,000 words, I wanted to expand and revise, add more meat to the bones. And I have, the story is now over 30,000. I didn't rush through the re-write.
Now for editing. Did your publisher do a clean, thorough edit? If you are not really revising the story much, why would you lay out extra money to hire an editor? A copy editor might be an option. (less money than a content editor) Regardless, having good old cousin Sally look over your manuscript is not a good decision. Also, don't finish your story one night and upload it the next. Let it percolate for a while, then look it over. Revise. More edits. And edit again. Hire an editor. Buff and polish until shiny.
Remember the costs of self-publishing can pile up with cover art, formatting, and edits. Can you expect to make your money back? Think realistically. Just because you're self-pubbing doesn't mean you are going to start raking in the dough. Make a budget for yourself. But don't cheapen your product. Make sure the edit is clean and professional as well as the cover and formatting. Slap-dash self-pubbed e-books look substandard and reflect on you and your 'brand'. (Ugh, that word!)
Here's what I said with the Timeless Heart blurb: Previously published. Re-edited, revised, and more than 7500 words added.
Also explore the pros and cons of the pre-order function. Worked great for me at Amazon, other vendors? Not so much. So I will adjust accordingly for the next release. Also be competitive in your pricing, but don't give the thing away, especially if you have costs to recoup.
In conclusion? Everyone has different thoughts on previously published books. Don't rush into it, (unless monetarily you must) do what's best for you. Maybe leaving it with the publisher works to your advantage. Great! But review your options often.