Try to upgrade firmware but not detected

[dr_nasseer]

This is my device description:
Model Name: ASUS X00LD
Firmware Version: WW. 14.0400.1708.160-20170911
Rooted or not: no
I tried to upgrade firmware using version WW-15.0400.1910.528 as provided on the web. I was downloaded it then copied to internal phone, but there is no reaction on system update detection such as icon notification on the drawer, even I restarted several times.
What should I have to do? I want to upgrade Bluetooth version instead. And also to follow the android development until the latest firmware.
Need solution...
Please help me.
Thanks

[Christine_ASUS]

Hi dr.nasseer
Thank you for your asking. To perform a cross-Android update, you need to update to the previous Android 7 version before the first Android 8 version. Kindly refer to the steps below
Auto update>WW-14.0400.1808.206>Manual update>WW-15.0400.1809.405>Auto update>Your preferred version
#ZD553KL Firmware Spot
https://www.asus.com/Phone/ZenFone-4-Selfie-ZD553KL/HelpDesk_BIOS/
#Manual Update Guide
https://www.asus.com/support/faq/1009748

[dr_nasseer]

Thank you for your guideline. Now my ZD553KL was upgraded to the latest firmware with Android 8.1.
But the next issues are:
1. The printing option is gone, I can't print any files directly to printer using USB cable.
2. Also it can't detect any flashdisk attached with OTG.
Would you please give me a solution. Thanks

[Christine_ASUS]

Hi dr.nasseer
Thank you for your reply. Can you received the notification while link on the USB? Try to tap the notification>tap "file transfer"
Besides, can you tell me where can you find the printing option? I found some apk from the website for the latest firmware version, please try the apks like AsusLauncherDev, MobileManager... except "UnlockTool".
ZenFone 4 Selfie (ZD553KL) Driver & Tools | Phone | ASUS Global

[dr_nasseer]

Thank you for your quick respons.
1. I can't receive that notification while connected via USB. Before upgraded, the USB flashdisk always detected.
2. When my firmware still Android 7.1, there is a printing option on the setting. But it's gone after upgraded. Then also can't detect USB Host Mode.
Would you have any suggestions?