If the display is normal, then maybe is the second situation of “b”, the thread wire were disconnect. If still showing 3 line, then is the first situation of “a”, the socket wire were fall out or break.
Swing Design 15 x 15 Swing Away 8-in-1 Heat Press - Pink
Combo 8 in 1 Heat Press Machine 12x15 Swing Away for T-Shirt Hat
MYSUB 8 in 1 Heat Press Machine Digital Combo Heat India
F2C Pro 5 in 1 Swing-Away Digital Transfer Sublimation Heat Press Machine Hat/Mug/Plate/Cap/T-shirt Multifunction New Black(5 in 1)
Heat Press Machine 12 x 15 Inch 8 in 1 Heat Press Sublimation Machine 360ø Rotation Swing Away 8 in 1 Shirt Printing Machine Dual-Tube Heating for DIY T-Shirts Cap & Mugs Blue
Combo Heat Press Machine - 8-in-1, 12x 15, 1250W, LCD, 360
Metal 3 In 1 Heat Press Combo Machine For T-Shirts Rocks Mugs
VEVOR 8 in 1 Heat Press 12x15 inch Heat Press Machine Digital Multifunctional Sublimation Swing Away Heat Press 360 Degree Rotation Heat Press Machine
VIVOHOME 8 in 1 Combo Multifunctional Swing Away Clamshell Printing Sublimation Heat Press Transfer Machine for T-Shirt Hat Cap Mug Plate 12 x 15 Inch Blue and Black
5 in 1 Heat Press Machine 12x15 inch Digital Tshirt Press Machine 360-Degree Swing Away - Black
Generic Heat Press- 8 In 1 Swing Away Digital Heat Press Machine