I have 4 Human characters created specifically in CotAB (didn't port them over from PoR). A human Paladin, Ranger, Cleric, and MU. I've completed the Dracondros encounter and have left Hap. I'm trying to dual class first the Paladin to a Cleric at level 7, but for some reason when I pick this option in Training, I get a response of 'character name DOESN'T QUALIFY'. I get this same response for the other 2 characters that I want to dual class, the ranger and cleric, but the Magic User is allowed to dual class....ironically, he's the only one that eventually I DON'T want to dual class. Has anyone else came across this issue that can tell me why they aren't qualified? All are Humans single class and currently at level
7. Thanks!

To dual class, a character needs 15 in the prime requisite of his old class, and 17 in the prime requisite of his new class.

So a Fighter dualing to Mage needs at least 15 STR and 17 INT.
To quote from the first Google result:
"The prime requisites for each class are:

- cleric: Wisdom
- fighter: Strength
- magic-user: Intelligence
- paladin: Strength and Wisdom
- ranger: Strength, Intelligence, and Wisdom
- thief: Dexterity "

Ranger to Mage is IMO the ultimate character in the Gold Box games, while I've never dualed a Paladin, since a Paladin is already kind of a Fighter/Cleric.

Yeah, I understand that prerequisite. Each of them have the prime requisite of their current class. It's not even letting me choose a class to change to...it's telling me the character 'DOESN'T QUALIFY' as soon as I click on the 'H' for Human Chang Classes in the Training Hall menu. I'm not even getting far enough for it to make that check since I've not tried to pick a class to dual to yet.

What are your characters' stats?
Can you possibly post screenshots?

Are the characters imported from Pool of Radiance? Imported characters some times have "issues".

Could it be that they have equipment readied not usable by the new class? Try unequipping all items.

It's not even letting me get far enough to pick a new class. I get 'char name DOESN'T QUALIFY' when I choose the 'H'uman Change Classes option from the Training Hall menu. I should have said also that I've unequipped everything they have and still didn't let me dual class them.

These characters are NOT imported from Pool of Radiance.
I took a SNIPIT of the stats, items, and screen that I'm getting the response from, but GOG won't let me attached that file type for some reason. (.JPG?!)
The Male Human Paladin, Lawful Good alignment has the following stats
STR 18(02)
INT 14
WIS 16
DEX 16
CON 16
CHA 17

Level 7 EXP 175000

AC -3 THAC0 10
HP 70 Damage 1D8+6

Weapon Long Sword +3 Frost Brand
Armor Plate Mail +3
Status Okay

For the record I also unequipped everything he owns and still get the response 'char name DOESN'T QUALIFY'

I tried to save it and attach the screenshot as a GIF, PNG, JPG, and HTML file and GOG wouldn't accept any of those fil formats. :(

Your Paladin needs 17 Wisdom to qualify for Cleric, but he only has 16.

Is Cleric that only option to dual class a Paladin to?

And by the way....where does it list what the new prime score has to be?

Should be able to dua to Mage too. If 17 Int. In the manual.

Sooooo, I created a new paladin with a Wisdom of 17 so that it could dual-class to a Cleric, but guess what...STILL said he was not qualified! His stats without any Ioun stones to modify are:
STR 18(80)
INT 14
WIS 17
DEX 13
CON 18
CHA 16

If I ready him with every IOUN stone I have available right now those change as follows:
DEX increases to 14
CHA increases to 17

Hmm...this means that either Paladins just can't dual class, or that the info I quoted was wrong and CHA is also a Paladin's prime requisite.
Not sure how you got 16 CHA; I thought you needed 17 CHA to become a Paladin in the first place.
Also, I'm pretty sure stat increases from spells and items don't work.

And your character also needs to be at least lvl 2 to dual, but since it's CoAB that should not be an issue.

Well, I assume paladins CAN dual class because I was dual classing him based on recommendations from others that have posted their best parties.
The manual said that only STR and WIS were primaries for paladin, however I did see that mention at the bottom of the paladin block about needing 17 CHA also. I wish to hell that the game wouldn't even let you create the paladin unless it had the required stats! I was only concerned in creating him that his wisdom was at least 17 to dual class to a cleric...so that's probably what's hanging it up! POS should have flagged that at character creation time if it wasn't valid!!!

Here’s from the AD&D 1st edition Player’s Handbook: Paladin is even mentioned here. Of course there is no guarantee SSI implemented the rules as written by the Gygax.