Sorry for the late reply
The thing is ur loss isn’t exactly the same on every epoch, it’s just approximately 0.69.
What I suggest is u initialize ur weights with xavier init.
Also since the relu activation only make outputs range from (0 to positive infinity), it won’t give room for negative inputs as it would approximate all negative inputs to zero, so I suggest u remove the relu activation for now and see how it works out.
It’s possible that ur neural network is not able to significantly differentiate patterns in ur data because ur data mostly consists of negative values and all negative values are approximated to zeros by relu activation, so it’ll just end up seeing alot of zeros than other numbers that significantly contribute to the image pattern.
This is just my speculation.
Hope this helps you .