Message type: E = Error
Message class:  FMCY - Copy budget data 
Message number: 066
Message text: Only Budgeting Process 'ENTR', 'RETN' or 'SUPL" are supported
Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of messages in the SAP system have a message text, however this is frequently insufficient to comprehend or resolve the problem.
To make things easier, more detailed information is frequently added to describe the issue, how to fix it, and the necessary steps or configuration modifications.
Unfortunately, there isn't any extra information in this error notice.
First, use our AnswerBot below to get a possible cause and solution (requires a premium subscription).
Also, review the in-depth Common Questions & Answers listed below; you could discover a solution there or be able to connect with others who have faced similar challenges.
You can also try searching the SAP support portal (support.sap.com) but you need a special user ID to access it. It is possible that an SAP support note exists that provides additional details about the mistake or even steps for fixing it.
The SAP error message FMCY066 indicates that the budgeting process you are trying to execute is not supported. Specifically, it states that only the budgeting processes 'ENTR' (Entry), 'RETN' (Return), or 'SUPL' (Supplement) are valid for the operation you are attempting.
Cause: This error typically occurs when: You are trying to execute a budgeting transaction that is not configured to support the process you are using. The budgeting process you are attempting to use is either not defined in the system or is not active. There may be a mismatch between the configuration settings in the system and the transaction you are trying to perform.
Solution: To resolve this error, you can take the following steps: Check the Budgeting Process: Ensure that you are using one of the supported budgeting processes ('ENTR', 'RETN', or 'SUPL'). If you are using a different process, switch to one of the supported ones. Review Configuration: Go to the configuration settings in SAP (transaction
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
FMCY065 Select a document number
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
FMCY064 Revaluation percentage &1 is greater than 100%
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
FMCY100 ****** RETRACTOR FOR BCS ********
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
FMCY101 No planning data found for BW System &1, query &2, derivation &3
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
Click on this link to search all SAP messages.