Cisco – Network does not work between Cisco router and HP switch

We have a Cisco router (887VA) supplied by a 3rd party. The supplier says its switch ports are simply untagged/access-mode. However our HP switch, which is connected to the Cisco router's switch through a port on the HP switch (j9772a), which untagged/access-mode refuses to work correctly.

We have verified that a laptop which directly connects to either the Cisco or the HP works as intended.

The strangest part is that if we use VLAN 1, untagged, on the HP-switch, the setup does work as intended. How can using a different VLAN, specifically VLAN 1, matter for the connection if its untagged? Is there magic between the two devices I should know about?

HP config:

hostname "SW02-E2"
trunk 45-46 trk10 lacp
stack join e0071b-0000
interface 44
   name "000 WAN"
   exit
snmp-server community "public" unrestricted
vlan 1
   name "DEFAULT_VLAN"
   no untagged 1-24,37-44,49-52,Trk10
   untagged 25-36
   tagged 47-48
   no ip address
   exit
vlan 2
   name "Default vlan2"
   untagged 37-42,49-52,Trk10
   no ip address
   exit
vlan 10
   name "Office network"
   untagged 1-24
   tagged 47-48,Trk10
   ip address 192.168.178.2 255.255.255.0
   exit
vlan 213
   name "VPN network"
   untagged 43-44
   tagged 7-8,10
   ip address 192.168.213.66 255.255.255.192
   exit
vlan 1000
   name "stacking"
   no ip address
   exit
spanning-tree
spanning-tree Trk10 priority 4
spanning-tree mode rapid-pvst
device-profile name "default-ap-profile"
   cos 0
   exit
password manager
password operator