That's how I've solve it. If this happen to you, you might try to install the bcryptjs package (yarn add bcryptjs) and replace:
yarn add bcryptjs
const bcrypt = require("bcrypt");`
by:
const bcrypt = require("bcryptjs");
Hope it will work for you too!
I had the same error, too. I didn't want to change bcrypt to bcryptjs. I uninstall bcrypt and installed it again, and the problem was solved.