@JJJJ How have you got the bed heater set up? Looking at the 'original' config from my machine, it's:
M307 H0 A119.9 C608.9 D1.4 S1.00 B1
The M307 B1 parameter on the end is for 'bang-bang' control, i.e. it turns on when it's not at temperature, and turns off when it is, so switching frequency is low. 'Bang-bang' control causes wider temperature swings, so usually B0 is used for PWM control of the bed. However, this comes at a much faster switching rate, set by the M950 Q parameter for the heater, which sets the PWM frequency in Hz.
It may be that you had the PWM frequency set too high for the SSR, which has either caused it to fail, or just to stay on. It's difficult to say what PWM frequency would work, as the 'Fotek SSR-100 DD' doesn't seem to be a current product, see https://www.fotek.com.tw/en-gb/product-category/144. The other SSRs in that range state a 'response time' of 1ms (millisecond). This might mean that it can switch at 1000 times a second (1000Hz), but realistically I'd tend to drive it at a much lower rate, eg 10Hz, as we suggest here: https://docs.duet3d.com/en/User_manual/Connecting_hardware/Heaters_bed#configuring-a-bed-heater
We also don't recommend this kind of SSR, see https://docs.duet3d.com/en/User_manual/Connecting_hardware/Heaters_bed#bed-heater-driven-using-a-solid-state-relay
Ian