USER Exit not declared in From pool RGGBS000 a

I have a problem concerning GCX2, Table t80d. on changing of the user exit program and then reverting back to the original.

After experimenting with an alternative user exit program , for GL, ie. Zrggbs000, we reverted back to the SAP delivered RGGBS00.

I am now getting the user exit not declared in the form pool errors.

i.e.

User exit UFP000 not declared in form pool RGGBS000.

Is there a way to get rid of those errors.

Or do I need to do something manually.

Thank you

Jeffrey