The T1200 is trying to boot from the floppy drive as it's showing the non system disk error and the drive works/disk is readable once the laptop boots; this would imply to me that the boot disk isn't bootable, or isn't compatible with the laptop.
Which boot disk image are you writing to the boot floppy?
The early Toshiba laptops use a proprietary floppy drive (well propriatary connector), they also use rubber belts which are prone to stretching with age. If you haven't replaced the belt yet it may be the cause (although unlikely as the drive reads fine once booted)
Gaming rig: Dell Dimension XPS T500 - PIII 500 - 288MB RAM - Voodoo3 3000 - SoundBlaster Live! Value - DVD-ROM - CD-RW - 3.5" 1.44 - 98SE & 2000 dual boot
A nostalgic pile of laptops from the late 80's to late 90s.