The error message: 'period depreciation transactions must be entered sequentially' is due to a month (period) of depreciation missing from the asset's activity.
For example if you have the asset's acquisition date as 08/01/02017, there has to be a period depreciation transaction listed for the month of August before they system will let you enter a period depreciation transaction for the month of September.
Steps to Duplicate1) Got to fixed assets module
2) Click Records > Assets
3) Open Asset record
4) Click on Activity Tab
5) Choose 'New Period Depreciation'
6) Transaction Type: Period Depreciation
Transaction Date: xx/xx/xxxx
7) Complete the GL distribution tab
8) Click Save and Close
9) Get error message