Help with a conditional format: VALUE error with named ranges

[DPeer]

I have been building a Gannt chart (mostly from an example on YouTube) and have come up against what I think is a simple problem, but can't get to the bottom of it. I'm using named cells and ranges, but am getting a "value" error in one formula. My thinking was that there was a problem with one of the named ranges links.
Anyway, I have attached the file for perusal. Any answers appreciated.

Change the setting on the "Settings" sheet by "weekends & holidays" to FALSE, and go back to the "Gannt" sheet. You will see that the date row gets a value error. Data used in the formula is the wrong type. Don't know why the chap that posted this didn't have the same issue.

[AliGW]

Administrative Note:

We would very much like to help you with your query, however the thread title does not really convey what your request is about. Tell us what you are trying to do, not how you think it should be done.

Please take a moment to amend your thread title. Make sure that the title properly explains your request. Your title should be explicit and not be generic (this includes function names used without an indication of what you are trying to achieve).

Please see Forum Rule #1 about proper thread titles and adjust accordingly. To edit the thread title, open the original post to edit and then click on Go Advanced (bottom right) to access the area where you can edit your title.

(Note: this change is not optional. No help to be offered until this moderation request has been fulfilled.)

[DPeer]

Madam:
I have changed the thread title, but I don't know how to explain it in a few words. It is an issue I'm having with conditional formatting which I laid out, I believe, quite well in the body of my thread. If this doesn't work for you, so be it. I have found this forum to be helpful in the past, and am appreciative.

[AliGW]

Please read the forum rule about titles. I have changed yours again to show what we mean. The rule is not meant to be unhelpful - quite the opposite, in fact. Your title should briefly summarise the issue. 'Conditional formatting' is not the issue, nor is it enough to tell us what you are trying to do. If we let it go, we'd have literally thousands of threads all with that same title, and all actually asking quite different questions. Thread titles need to work also in an Internet search: clearly 'conditional formatting' would not find this thread for anyone else having an issue with named ranges in CF generating an error message, would it?

I hope you understand.

[AliGW]

Your holidays named range is at fault. Change it to this:

=Settings!$C$17:$C$94