This error message is wrong:

No subnet declaration for wlp2s0b1 (no IPv4 addresses).
** Ignoring requests on wlp2s0b1.  If this is not what
   you want, please write a subnet declaration
   in your dhcpd.conf file for the network segment
   to which interface wlp2s0b1 is attached. **

Proof:
$ make dhcpd #will produce this message
$ make w r dhcpd #will not produce this message, and work fine.

The error is the interface is not up, not that the dhcpd.conf needs to
be changed!

Dear submitter,

as the package isc-dhcp has just been removed from the Debian archive
unstable we hereby close the associated bug reports.  We are sorry
that we couldn't deal with your issue properly.

For details on the removal, please see https://bugs.debian.org/1143544

The version of this package that was in Debian prior to this removal
can still be found using https://snapshot.debian.org/.

Please note that the changes have been done on the master archive and
will not propagate to any mirrors until the next dinstall run at the
earliest.

This message was generated automatically; if you believe that there is
a problem with it please contact the archive administrators by mailing
ftpmaster@ftp-master.debian.org.

Debian distribution maintenance software
pp.
Thorsten Alteholz (the ftpmaster behind the curtain)