Site: RegionsBill pay not working. Error code 4100. Has been nonfunctional since last Thursday. Reported 3 times but remains unresolved. Add new comment Comments I have been experiencing the same problem myself. I have called multiple times with no resolution. reply Add new comment Your name * E-mail * The content of this field is kept private and will not be shown publicly. Comment * Notify me when new comments are posted 21mHTd Enter the code above * Enter the code without spaces.