[I see you've edited your post to indicate that you've solved the problem - nice! - but since I had composed this post already and was just about to submit it, I'll do that anyway. It might help confirm/update your understanding.]
(2020-04-04, 04:09 AM)CandleJack Wrote: [ -> ]I did not change the expressions.
OK, you need to do that, because the one you've got now means that any user input for that field needs to exactly match "cheight" - and, obviously, that's not what you want.
(2020-04-04, 04:09 AM)CandleJack Wrote: [ -> ]Is the "regular expressions" the equivalent to the field IDs like what I've been finding in older posts for the previous version of myBB?
Regular expressions are special patterns according to which values are matched. You can, for example, with a regular expression create a pattern that matches values that are only digits (which would be more appropriate for your custom "height" field, but maybe not even exactly what you want). If you
did want to match like that, then you would enter something like this in the Regular Expression field:
\d+
With that regular expression, any value that the user entered that was
not a string of one or more digits would be rejected with the error message you're currently seeing. Right now, though, any value that the user enters that is
not exactly equal to "cheight" is being rejected with the error message you're seeing. Again, this is not what you want.
Wikipedia has a page on regular expressions in case you are interested in learning more (though I have not yet read it myself):
https://en.wikipedia.org/wiki/Regular_expression
(2020-04-04, 04:09 AM)CandleJack Wrote: [ -> ]If I don't set the expressions, how am I going to figure out the field ID so I can set them in the custom profile I've created?
I'm not sure what you mean. If you choose "Yes" to the "Display on profile?" setting question (which you have done), then the fields show up when viewing a given user's profile under "Additional Info About [username]". Do you want something more than / different to that to occur? If so: what exactly are you trying to achieve with your custom profile fields?
(2020-04-04, 04:09 AM)CandleJack Wrote: [ -> ]I have changed all the character lengths to the max. That did not change the problem.
Right, because the (current) problem is that you have set a value for the Regular Expression field that is highly, highly unlikely to ever match anything a user might enter.