Are you sure it was even on in the first place ?
pi@arcade:~ $ iw dev
phy#0
[..]
Interface wlan0
[..]
pi@arcade:~ $ iw dev wlan0 get power_save
Power save: on
pi@arcade:~ $ sudo iw dev wlan0 set power_save off
pi@arcade:~ $
pi@arcade:~ $ iw dev wlan0 get power_save
Power save: off
I believe the Pi-OS distro default disabled power saving a long time ago for on-board WiFi ... but I could be wrong.
What distro do you have running ?
hostnamectl | tail -3
And maybe below is nicer for in the /etc/network/interfaces file:
allow-hotplug wlan0
iface wlan0 inet manual
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
wireless-power off
Above allows dhcpcd5 to UP the interface and assign it an IP:
pi@ph5:~ $ tail /etc/dhcpcd.conf
[..]
interface eth0
static ip_address=10.0.0.4/24
static routers=10.0.0.1
static domain_name=dehakkelaar.nl
static domain_name_servers=10.0.0.1
pi@ph5:~ $ sudo service dhcpcd restart
pi@ph5:~ $
pi@ph5:~ $ journalctl -u dhcpcd
[..]
Jan 29 23:04:10 ph5 dhcpcd[21014]: eth0: using static address 10.0.0.4/24
Jan 29 23:04:10 ph5 dhcpcd[21014]: eth0: adding route to 10.0.0.0/24
Jan 29 23:04:10 ph5 dhcpcd[21014]: eth0: adding default route via 10.0.0.1