Yup! You are right, I plug it to PC just for testing purpose.
Because it can't seems to work on Maxis' TP-Link router so I try it on PC.
That was last night when Maxis Fibre were down for many people, so I have to try hard for this backup SIM to work.
There was once when I plug it to PC, it seems so have connection, then it ask new software is available and if I would like to update.
I clicked [Yes] then... never get it to work again since then...
The update should came from either Maxis or ZTE, I can't tell when the message simply pops-up just like that. 

for those with dongle that has been updated and unable to connect anymore, try these steps:

1. browse to the dongle IP address using firefox
2. go to Settings -> Dial-up settings
3. right click in the page -> Inspect Element
4. search for #auto_mode, double click on disabled="" on the highlighted line, delete it, press enter
old value =

new value =

5. Automatic radio button is now enabled, click on it
6. search for apply, delete disabled="" as well
old value =

new value =

7. Apply button is now enabled, click on it, you should receive success message

Now, the dongle should be usable again with maxis router archer c5v and should auto connect if fiber connection is down.