What does the bill of sale say you bought? In all honesty, you probably will not be able to get clean title and the city may require you to remove the home (or demolish it).
If there is no label number, you need to apply for a "seal number" which is the ID number for a home with no label number. Once you have a "seal" you can apply for title (SOL or Statement Of Location).
In order to get a SOL you need to tell the TDHCA whether the home was moved for this sale. If it was moved, they will need the mover's permit (called a Form T) and a statement from the county (called a Form 1076) where it resided on 1/1/2017 stating that 2017 taxes have been escrowed (the bills come out in October).
If it was not moved, then you need the Form 1076 from your County.
If it moved from a different county, the taxes should have been paid in the county where it was on 1/1/2017 in order to get a moving permit. If it was moved without a permit, the mover should be liable (but good luck chasing him down, or the seller).
IF you can figure out where it was on the tax rolls before it was moved, there should be a record of its tax status. As the new owner, you will have to pay any back taxes or you will not be able to get "clean title." Assuming you do get the Form 1076, you may be able to tell the TDHCA that you don't know who moved it (and avoid the hassle of documenting the Form T).
Cities can prohibit "mobile homes" (Pre-HUD homes i.e. pre-1976). You may have bought one in which case you'll have to sell it to someone else who takes it off your hands, or demolish it. Or it may be post-1976 but not a HUD-code home.
If it's really a HUD-code manufactured home but just you can't find the info, you'll probably have to explain that on the form Form 1008 that @jhutson posted. If the TDHCA believes you then you can/will get the seal #. (*I have never tried this). That's probably your best shot at a way out of your mess. Otherwise you have about $3k demolition bill to show for all your hard work (or, you might be able to sell it as "business use" if you can get a seal #.)