https://userapps.support.sap.com/sap/support/knowledge/en/2464694
2464694 - Unable to maintain Account Range in 'Manage Posting Periods' Fiori app (F2293)
Your system is on SAP S/4HANA Cloud Public Edition 1702, When using the Fiori app "Manage Posting Periods" you are unable to maintain / change an Account Range...