What causes this issue?

Due to changes in the depreciation parameters, the conversion year
may have also been affected.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Please check whether conversion year &V1& is still valid following
your changes to the master data. Once a conversion year has been
entered in the depreciation area for an asset, it can no longer
be changed automatically.

Error message extract from SAP system. Copyright SAP SE.