I am not an attorney and this is not "professional advice."

Consult a lawyer.

If you get involved with a partnership ever again, get an operating agreement in place and TALK ABOUT SEPARATING at the beginning. Get it figured out immediately. Be up front with it: "We should talk about what happens if one of us dies. Or wants to move on." It's not offensive, or confidence-gutting...it's smart (as you probably now see.)

Generally speaking, an agreed-upon independent third party firm would assess the value of the company. This firm would be named in the operating agreement provisions so there wouldn't be bickering at the time of separation.

Another typical provision is that partners have first right of refusal on share sales.

But since you don't seem to have such an agreement in place, it's probably going to be tough for you now. The more you fight the more the other shareholder is going to fight back.

Consult an attorney. Find out if there are any restrictions on selling your shares.

My guess is that with a negative cash position due to debt, the company isn't worth a whole lot. You may be able to have a value assessed based on revenue...but if you leave, how much of that goes with you? Is the business model based on repeat customers, or one-time sales? You need more expertise than a Clarity answer to solve this one.

And remember, the more mean-spirited you approach this question, the more resistance you will get.

My opinion--which again is not "professional advice" and is merely for discussion--is for you to quietly discover your options by consulting an attorney and accountant good at digital business evaluation (most are not), and wait for the company to return to profitability.