I experienced same issue with csv import again. It seem like no import is allowed during first few days of the month: I have tried on 01.02.2018, 02.02.2018 & 03.02.2018 with no luck. Everytime I get "0" error message.
I have made many trials and here are the conclusions:
- it is not file permissions issue
- it is not specific to any particular csv file: previously imported files doesn't import and dummy files doesn't import
- changing system date (without reset) doesn't help in most cases
- changing system date + system reset work fine - allow to import, even if you change the date back to original just after reset.
So on 02.02.2018 I changed the date to 05.02.2018, reset the system (Windows 8.1), changed the date back to 02.02.2018 and the import was working. After all imports I reset the system again and the problem was visible again. Only the date during system start is important!
I can provide you more info if you need. Please fix it.