Possible causes for incorrect dates are as follows:

1. The plan specifications for eligibility & entry dates are not entered correctly in the compliance software.
2. If there's a special participation date under Eligibility, the date may be incorrectly formatted. e.g. 'January 1, 2018' rather than '01/01/2018'.
3. An override is set under Scrub/Eligibility Parameters Overrides, e.g.'Override initial eligibility status/entry date:' If this is set to Yes the software will not calculate the dates - only set this override when you are uploading the dates.
4. Individual eligibility overrides may be set for the participant(s) in question; to verify this, add the grid '* ftw Override Initial Eligibility/Entry dates' on the Other Imports/Exports/Reports screen; you can see whether any individual overrides are set to yes.
5. There may be incorrect data on the census, either in the current year or a previous year.
6. The first year in ftwilliam, the calculations are based on the assumption that hours, compensation etc were the same in previous years as in the current year. If you have people who, say terminated in the current year, and worked fewer than 1000 hours, the assumption will be that they worked the same number of hours in previous years. If there's a 1000 hours requirement for eligibility, you will need to add the appropriate prior years of service  before running the data scrub.
7. If you converted data from another record keeping system, you likely loaded eligibility & entry dates on the conversion file. You should go back to the conversion year and check the dates on the file. If there are bad dates you will need to re-upload the corrected conversion file (check Yes to reset eligibility), then re-run the scrub.

Also see the following articles:

Eligibility - First year on ftw, ppt worked 1000 hrs this year but fewer in prior years so shows as eligible when he should not be.

Eligibility - First year on ftw, ppt worked fewer than 1000 hrs this year but more in prior years; shows as not eligible when she/he should be.

Recalculating Eligibility & Entry Dates.