MD5 hash key too long - but no hash

[shqipo]

I have two sites, same authorize.net account. One is working OK. The other one was working OK until it got hacked. After I recovered and updated to 1.3.9h, authorize.net doesn't work. It says MD5 hash key too long. However, when I go to edit it, there's no option for that, just an empty field. I do enter my MD5 hash key there, but it doesn't record anything. See attached screenshots.

[DrByte]

Those are classic symptoms of installing a newer module over an older one, but not first writing down all the settings and clicking Remove and then clicking Install and reconfiguring it.
The ZC upgrade documentation in the /docs/ folder makes mention of the need to do that.

[shqipo]

Thank you Dr. Byte. Now that I made that mistake, is there a way to fix it?

[DrByte]

Ya. As I said, fix it by: first writing down all the settings and clicking Remove and then clicking Install and reconfiguring it.