AFAB issue after upgrade SAP 4.0 to ERP 6.0 EHP 7

Dear Gurus,

i encountered an issue after upgrading SAP 4.0 to ERP 6.0 EHP 7 regarding standard t-code AFAB.

Customizing in 4.0 is the same of 6.0. IN 4.0 AFAB works fine while in 6.0 i've met the following error:

"Account 120200100 in company code xxxx cannot be directly posted to"

AO90 of the asset class:

FS00 details for account 120200100:

Someone has ever met this issue or knows how to solve it?

I can't understand why in 4.0 it works while in 6.0 not.

(if in OAMK i unset the account as reconciliation account then i experience the following error: Account 120200100 is not a reconciliation account)

Thanks

Gianni