Can I convert an LLC to an S-corporation in Maryland (as part of converting the company to a 501(3)(c) non-profit)?

You cannot convert an LLC directly into a corporation. You would be best advised to establish a new nonprofit corporation and transfer all of the assets of your LLC to the new corporation and then wind down the LLC. You can keep the same name as long as there is no corporation with the same name. You should contact an attorney to assist you with this matter.

I agree with all comments of the prior attorney. Technically the IRS doesn't "grant" non-profit status so much as establish mandatory procedures for "recoginzing" that status. Your form 1023 will probably be rejected because LLCs are for-profit entities owned by their members; while non-profits can certainly be governed and run, they cannot be owned and the ownership issue will probably kill your 1023. "S-corporation" status under subchapter S of a title of the Internal Revenue Code is a federal tax status for for-profit corporations that (if qualified) make a certain election by form 2553 to have their corporate profits pass through to their stockholders' income tax returns in proportion to their shares. S Corp status is absolutely incompatible with non-profit status; non-profit corporations are governed under subchapter F of the same title, but most people refer to section 501 rather than its parent subchapter F (and probably because "F" and "S" sometimes sound the same to some people.) I implore you in the strongest language to get a tax attorney immediately. Your decision to file form 1023 wasted your money; tax attorneys cost money but stand behind their work professionally and generally have malpractice insurance. Please do not delay and good luck.