Hi Mathivana,
I had faced these issue several time. As per SAP standard logic whenever you saved order in CRM it replicate immediatly in ERP till that time the order will be locked for any further change in CRM to save transaction data intigrity. The lock gets removed once the CSA queue(notification) from ERP update in CRM than unlocked.
You check the in SMW01 transaction and perform search with order number you will find Bdocs are in Intermediate stage(I can't tell reason as it can be so many reason why Bdocs get stuck) -Select and activate the Bdocs once again if you are lucky and it activated your order till be unlocked.
Or else user report most common for this issue "CRM_CHECK_DISTRIBUTION_STATUS" pass order number number and document type to unlock distribution than you will be able to change order.
100 % sure shot answer. Appriciate if points alloted
Thanks,
prem