Hi @dsesno. Let me start by saying: UGH! This is must be so frustrating.
It is, unfortunately, how the IRS rules work around deductions – if you had a plan and any contributions were allocated to your account for the plan year, you’re considered “covered by a retirement plan at work” and that means the income limits for deducting your IRA contributions come into play.
Based on what you’ve said, it does sound like a SEP IRA could be an option for you. (A solo 401(k) typically has to be set up by the end of your business’s taxable year, which means that deadline has likely passed.) But given that you have a fairly complicated situation, I would really advise talking with a CPA who is familiar with these plans and can help you make the most of your options. The deduction formulas for both plans are fairly complicated, and working with a pro will be worth it.
Here are our articles on SEP IRAs and Solo 401(k)s: