Here is what "might" work. Drain the tank. Clean the seam from one end to the other. Do not use alcohol or vinegar. Water and a lot of scrubbing. Use a syringe bottle with the thin needle and try to fill the seam leak area with some solvent (weld-on #4 will work). Get a piece of square acrylic rod 2x thicker than the tank acrylic and weld it to the seam (weld-on # 4 will work). If you don't have experience with acrylic, have a professional do it.
If it was me I would get my money back.
If it was me I would get my money back.