The error [-11414] Buffered Point does not accept new events is being thrown because you are trying to write to a PI Point on which the PI Buffer Subsystem has a lock. This typically happens when trying to write using a non-buffered application to a PI Point that is being written to by another application going through the PI Buffer Subsystem. More information can be found in this KB: https://techsupport.osisoft.com/Troubleshooting/KB/KB00093/.
If you are trying to write from Excel, you could enable the PI Buffer Subsystem and this should work fine.
What version of PI Manual Logger are you running? The UI in the newest version is much better.
You could also use the PI Interface for UFL: https://techsupport.osisoft.com/Downloads/File/a10264b4-0683-45be-b054-3fde92509f7d ? Or alternatively, write a PowerShell script to parse the file and write to the PI Data Archive: https://techsupport.osisoft.com/Documentation/PI-Powershell/title.html