[FIXED] Touch pad stopped working (Aspire ES 15 ES1-523-40MT)

[Clickbait]

Exactly what it says on the tin. The touchpad is turned on but it doesn't work. It stopped working after an update. I don't know which one did it.... And I did several dozen updates in one go...

Machine/System Details:

System:
Host: anon-Aspire-ES1-523 Kernel: 4.15.0-45-generic x86_64 bits: 64
compiler: gcc v: 7.3.0 Desktop: Cinnamon 4.0.9
Distro: Linux Mint 19.1 Tessa base: Ubuntu 18.04 bionic
Machine:
Type: Laptop System: Acer product: Aspire ES1-523 v: V1.02
serial: <filter>
Mobo: Acer model: TRICERA_CZL v: V1.02 serial: <filter>
UEFI [Legacy]: Insyde v: 1.02 date: 09/19/2016
Battery:
ID-1: BAT1 charge: 16.3 Wh condition: 32.1/37.3 Wh (86%)
model: COMPAL PABAS0241231 status: Discharging
CPU:
Topology: Quad Core model: AMD A4-7210 APU with AMD Radeon R3 Graphics
bits: 64 type: MCP arch: Puma rev: 1 L2 cache: 2048 KiB
flags: lm nx pae sse sse2 sse3 sse4_1 sse4_2 sse4a ssse3 svm
bogomips: 14372
Speed: 1155 MHz min/max: 1000/1800 MHz Core speeds (MHz): 1: 1159 2: 1195
3: 1187 4: 1178
Graphics:
Device-1: AMD Mullins [Radeon R3 Graphics] vendor: Acer Incorporated ALI
driver: radeon v: kernel bus ID: 00:01.0
Display: x11 server: X.Org 1.19.6 driver: ati,radeon
unloaded: fbdev,modesetting,vesa resolution: 1366x768~60Hz
OpenGL: renderer: AMD MULLINS (DRM 2.50.0 4.15.0-45-generic LLVM 7.0.0)
v: 4.5 Mesa 18.2.2 direct render: Yes
Audio:
Device-1: AMD Kabini HDMI/DP Audio vendor: Acer Incorporated ALI
driver: snd_hda_intel v: kernel bus ID: 00:01.1
Device-2: AMD FCH Azalia vendor: Acer Incorporated ALI
driver: snd_hda_intel v: kernel bus ID: 00:14.2
Sound Server: ALSA v: k4.15.0-45-generic
Network:
Device-1: Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet
vendor: Acer Incorporated ALI driver: r8169 v: 2.3LK-NAPI port: 2000
bus ID: 01:00.0
IF: enp1s0 state: down mac: <filter>
Device-2: Qualcomm Atheros QCA9377 802.11ac Wireless Network Adapter
vendor: Lite-On driver: ath10k_pci v: kernel port: 2000 bus ID: 02:00.0
IF: wlp2s0 state: up mac: <filter>
IF-ID-1: tun0 state: unknown speed: 10 Mbps duplex: full mac: N/A
Drives:
Local Storage: total: 238.47 GiB used: 44.44 GiB (18.6%)
ID-1: /dev/sda vendor: Kingston model: RBUSC180DS37256GH size: 238.47 GiB
Partition:
ID-1: / size: 226.17 GiB used: 44.36 GiB (19.6%) fs: ext4 dev: /dev/dm-1
ID-2: /boot size: 703.5 MiB used: 78.7 MiB (11.2%) fs: ext4 dev: /dev/sda1
ID-3: swap-1 size: 6.96 GiB used: 0 KiB (0.0%) fs: swap dev: /dev/dm-2
Sensors:
System Temperatures: cpu: 58.9 C mobo: N/A gpu: radeon temp: 61 C
Fan Speeds (RPM): N/A
Info:
Processes: 214 Uptime: 10h 16m Memory: 6.77 GiB used: 1.89 GiB (27.9%)
Init: systemd runlevel: 5 Compilers: gcc: 7.3.0 Shell: bash v: 4.4.19
inxi: 3.0.27

[thx-1138]

...go into your BIOS/UEFI, see if your touchpad is set to 'Advanced', set it to 'Basic' instead...

[Clickbait]

I checked BIOS, it's already set to 'basic'...

[thx-1138]

...try reverting to a previous kernel, ie. 4.15.0-43 (or even better, if you remember such, to whatever revision you were using before).
It's not that many things that can break touchpad's functionality really, it's either the kernel (most likely...), or libinput driver / libs.
Considering this laptop's history with the touchpad misbehaving every now & then, i'd probably bet in the kernel revision.

Open Update Manager - View Kernels - Install...on reboot, press Shift (or ESC if that doesn't do it),
to bring up grub2's menu, select the previous kernel revision in question.
If you find that the touchpad works, remove the newer revision (grub boots by default in the newer kernel it finds installed).

...the other thing you could alternatively try out is the following:
xed admin:///etc/default/grub
Modify / add in the line there as follows:

GRUB_CMDLINE_LINUX_DEFAULT="i8042.reset i8042.nomux i8042.nopnp i8042.noloop quiet splash"

Save, run sudo update-grub, reboot.
Supposedly the i8042.nopnp option in specific might have some extra chance on this laptop for the touchpad to be detected,
but i wouldn't really bet on it...i'd personally focus more on trying to find a previous kernel revision that worked properly.

EDIT: ...well, this is obvious, but since it's frequently forgotten / overlooked...
make sure you haven't accidentally turned off the touchpad via hotkeys, i believe they should be Fn+F7 in that model.

[Clickbait]

...I turned the bloodthing thing off somehow... Fn + F7 fixed it...

Well... shit.