SMTP Issues in 18.0.1

So, I have an odd thing happening. I have 2 instances of Dolibarr running, one as my test bed (18.0.1) and another as my production version (17.0.1). I recently upgraded my test bed from 17.0.1 to 18.0.1 and was starting the process of setting up SMTP within Setup>Emails> and noticed that when I attempt to use the SMTP/SMTPS socket library, I am putting in the SMTP password, I click save and it changes the password. In fact, when I click on ‘reveal password’ within Firefox it gives me this error----
“Error dolDecrypt decrypt key is empty”
I have attempted to change this several times, but it keeps reverting back each time. Not sure what could be causing this. Any help would be appreciated as this is the only hiccup that is preventing me to upgrading the production server to 18.0.1.

Hello,

Could be linked to this :

Sensitive datas like keys in setup pages, that need encyption (for example the API keys of users, the CRON security key, the keys into the Stripe module, or
external modules setup pages that store sensitive keys or password), are using the $dolibarr_main_instance_unique_id as part of the key for encryption. So,
if you restore or duplicate the data from another instance dump, you must also update this parameter in ther conf.php file to allow decryption in the new instance, or
better, you must reenter the sensitive data into the setup pages of the new instance to resave them correctly.
Note that to find all the parameters that are encrypted into the setup database, you can do a “SELECT * FROM llx_const WHERE value LIKE ‘%dolcrypt%’;”

Source : https://github.com/Dolibarr/dolibarr/blob/18.0.1/ChangeLog

Have you a $dolibarr_main_instance_unique_id defined in conf.php ?