This was almost certainly not your issue. In fact, what you have done is not recommended in mot cases. It doesn’t cause any harm in this particular case, but using a /8 is not necessary and typically bad form for a variety of reasons.
Try changing it back to /24 (255.255.255.0) and rebooting again. You will find that it will work.
I suspect it was simply the reboot that fixed your issue, especially if you made changes and tested without a reboot earlier.