What are you trying to Blacklist? If Chrome, you could run into issues on Fully Managed devices and I have seen the Blacklist hang in pending status in those situations. The SOTI Lockdown utilizes the system WebView to render its HTML and when you Blacklist Chrome the WebView implementation changes from Chrome to the default WebView on newer GMS devices. This ultimately can create a conflict between your Lockdown and the Blacklist since the Blacklist is usually applied while in Lockdown mode. 

There are several apps to be blacklisted. But i think none of them is causing problems to be blocked, because, the rule is able to be installed but often keeps hanging.

---SIM Toolkit

com.android.stk

---System Apps

com.google.android.gm

com.google.android.apps.docs

com.android.email

com.google.android.talk

com.google.android.videos

com.google.android.music

com.android.soundrecorder

com.google.android.youtube

com.google.android.apps.babel

com.google.android.apps.dynamite

com.android.dreams.phototable

com.android.wallpaper.livepicker

com.google.android.keep

----Zebra

com.symbol.activeedge

com.symbol.batterymanager

com.zebra.hotswap

com.symbol.btapp

com.symbol.devicecentral

com.symbol.simulscan.demo

com.zebra.licenseuiapp

com.symbol.pttexpress

com.symbol.rxlogger

com.symbol.rxloggerutility

com.zebra.tc51ug

com.zebra.smartmu.app

com.zebra.bluetooth

---Samsung

com.facebook.katana

com.samsung.android.game.gamehome

com.sec.android.app.sbrowser

com.microsoft.skydrive

com.sec.android.app.samsungapps

com.linkedin.android

com.sec.android.app.fm

com.samsung.android.bixby.agent

com.samsung.android.email.provider

---Lenovo

com.microsoft.bing.wallpapers

com.focaltech.ft_terminal_test

com.microsoft.office.outlook

com.google.android.apps.youtube.music

com.caf.fmradio

com.lenovo.tab_m10_hd

com.tblenovo.lenovotips