I same boat.

New 12 digit TNB account number is not accepted in uobpayonline. 

You have two option
1) if u want to split bill- you can still pay in uobpayonline using old 14 digit tnb account number. *tnb still accept the old number until 31 Oct 2016 only.
2) option 2 is that you can manage your tnb account in tnb new e-portal website . This cannot split the bill.
Https://www.my tnb.com.my/User/login
If u are owner of tnb account ..u need to key in IC number therefore they will show Full address.
If u are not owner , u can choose to add as non owner account where u cannot see details of owner full address.
It does not make any different owner and not owner.

One thing that in TNB website u cannot split the bill. U can only pay what is due in one transaction using credit card or online banking.

The green button will appear when amount payable . If the green button does not appear therefore meant that the tnb have not Gen the bill and no bill due .

so far, adding 12 digit account in uobpayonline does not encounter any problem.

only is when proceed to make payment with 12 digit account no. ,will encounter message of  "invalid account no. " and cannot proceed further. Tried at 27 July also same. Have send email to uob, yet no reply until today.

previously myTNB Mobile App already not eligible.

since the new myTNB Web Portal seems to be using same payment gateway, so you're the first (i think) confirming this payment channel not tagged as UTILITIES category.

btw, you chose UTILITIES category for your Wise card, right?
unlikely, because Wise card depends on the exact MCC registered to the cc terminal.

petrol kiosk has different MCC than service station/counter; and Wise only detects petrol kiosk MCC. read the T&Cs.

Because your amount is less than rm50

Call CS to transfer to your other HLB card, if you have any or they can arrange to transfer to your savings account even not from HLB but you have to pay for RM 2. This is what the CS told me but transferred to my MACH card.