Use-server acl urlp test not working

Help!
1

using HA-Proxy version 1.8.8-1ubuntu0.4 2019/01/24

the following backend tests for a url query and selects server … however none of the tests work and the default is always selected

e.g. https://foobar-nd.ddns.net?netdata_server=openvpn should select
use-server netdata-openvpn if { urlp(netdata_server) -m str openvpn }
server netdata-openvpn 192.168.1.235:19999 check weight 0

any ideas what i’m doing wrong ? thanks in advance

backend netdata-backend
	mode http
	http-request set-header X-Forwarded-Port %[dst_port]
	http-request add-header X-Forwarded-Proto https if { ssl_fc }

	use-server netdata-openvpn  if { urlp(netdata_server) -m str openvpn }
	server netdata-openvpn  192.168.1.235:19999  check weight 0

	use-server netdata-poolside  if { urlp(netdata_server) -m str poolside }
	server netdata-poolside  192.168.1.18:19999 check weight 0

	use-server netdata-rosegarden  if { urlp(netdata_server) -m str rosegarden }
	server netdata-rosegarden  192.168.1.170:19999 check weight 0

	use-server netdata-stage  if { urlp(netdata_server) -m str stage }
	server netdata-stage  192.168.1.174:19999 check weight 0

	use-server netdata-ha  if { urlp(netdata_server) -m str ha }
	server netdata-ha  192.168.1.123:19999 check weight 0

	use-server netdata-pihole  if { urlp(netdata_server) -m str pihole }
	server netdata-pihole  192.168.5.2:19999 check weight 0

	use-server netdata-unifi  if { urlp(netdata_server) -m str unifi }
	server netdata-unifi  192.168.1.16:19999 check weight 0

	use-server netdata-unms  if { urlp(netdata_server) -m str unms }
	server netdata-unms  192.168.1.207:19999 check weight 0

	use-server netdata-firepit  if { urlp(netdata_server) -m str firepit }
	server netdata-firepit  192.168.1.200:19999 check weight 0

	use-server netdata-greenhouse  if { urlp(netdata_server) -m str greenhouse }
	server netdata-greenhouse  192.168.1.187:19999 check weight 0

	use-server netdata-fireplace  if { urlp(netdata_server) -m str fireplace }
	server netdata-fireplace 192.168.1.201:19999 check weight 0

	use-server netdata-genmon  if { urlp(netdata_server) -m str genmon }
	server netdata-genmon  192.168.1.198:19999 check weight 0

	use-server netdata-gym  if { urlp(netdata_server) -m str gym }
	server netdata-gym  192.168.1.158:19999 check weight 0

	server default 192.168.1.207:19999 check