My 2015 laptop Inspiron 5558 was working just fine today morning without any issues. Dell update manager another pathetic application by Dell was not giving any updates information on my machine since 1 year now so I decided to see some old dell community threads. There someone mentioned about another pathetic application from Dell "Dell Support Assist" to fix it and the result is that my laptop is not at all booting up. When turning on nothing displayed on monitor however keyboard backlit is on and charging light keeps on blinking white. I cannot believe this that a product build to fix things actually messed it up. How is Dell still functioning I have no idea. Now Dell my service warranty is long gone (December 2017) so I can only request you to fix this problem you created for me.
What is your Windows operating system (if Win 10 please include your version and build at Settings | System | About | Windows Specifications), and do you still have the original hardware (hard drive, network adapters, graphics card, etc.) that shipped with your Inspiron 5558 from the factory? Do you have the Dell Inspiron 5458/5558/5758 System BIOS vA18 (released 19-Feb-2020) that is recommended on the support page <here> for your Inspiron 5558? If you aren't sure open a Run dialog box, enter msinfo32 to open your System Information panel, and look for the “BIOS Version/Date” field.
Can you boot up your computer in Safe Mode? See the instructions in the BleepingComputer tutorial at How to Start Windows in Safe Mode. Safe Mode only loads the minimum system files and drivers that are required for the operating system to work (e.g., without loading third-party programs like your Dell utilities) and if you suspect that a recent update to Dell Update v4.x or SupportAssist v3.x is preventing your computer from booting up in normal mode then you should be able to boot up in Safe Mode and uninstall this software at Control Panel | Programs | Programs and Features.
The support page <here> for your Inspiron 5558 shows that Dell has not released any software or drivers for that model since 04-Jun-2021, which would explain why Dell Update and/or SupportAssist have not detected any available updates for your computer for over a year. If you go to https://www.dell.com/support/home/en-us?app=products and enter your unique Service Tag you should be automatically directed to the support page for your Inspiron 5558, and when you click on the Drivers & Downloads tab and expand the Find Drivers section it should only show the list of updates recommended for your specific Service Tag. Note that the Dell Update Application for Windows 10 v4.2.1 listed on your support page (Dell-Update-Application-for-Windows-10_YGN8R_WIN_4.2.1_A00.EXE) is a Universal Windows Platform app that requires a Win 10 OS, while Dell Update v4.2.1 (Dell-Update-Application_889VD_WIN_4.2.1_A00.EXE) is an older W32 style of installer that is compatible with Win 7 SP1 to Win 10. The minimum system requirements for the latest SupportAssist v188.8.131.52 (released 23-Jun-2022) are posted <here> (i.e., Win 10 or Win 11, Microsoft .NET Framework 4.7.2, plus a new requirement for .NET Core Runtime v5.0.x).
Also note that several users have reported issuing installing and/or running the latest SupportAssist v184.108.40.206 - see GlobalEngineer's 20-Jul-2022 SupportAssist Fails to Launch for one example. If you have a Win 10 OS (your support page says the Inspiron 5558 cannot run Win 11) then I would suggest that you uninstall SupportAssist until Dell fixes some of the bugs in SupportAssist v220.127.116.11. Given that Dell hasn't posted a new update on the support page <here> for your Inspiron 5558 for over a year (including the Dell Update Windows Universal v4.5.0 app recommended for my Inspiron 5584), even Dell Update v4.2.1 will be of little use on your computer. Going forward, you might want to uninstall both SupportAssist v3.x and Dell Update v4.x and just check the Inspiron 5558 support page on occasion to see if any new updates have been posted for your system. ----------- 64-bit Win 10 Pro v21H2 build 19044.1826 * Firefox v103.0.0 * Microsoft Defender v4.18.2205.7-1.1.19400.3 * Malwarebytes Premium v18.104.22.168-1.0.1716 * Macrium Reflect Free v8.0.6867 * Dell SupportAssist v22.214.171.124 * Dell Update Windows Universal v4.5.0 * Dell Fusion Service v126.96.36.199 * Inspiron 5583/5584 BIOS v1.18.0 Dell Inspiron 15 5584, Intel i5-8265U CPU, 8 GB RAM, 256 GB Toshiba KBG40ZNS256G NVMe SSD, Intel UHD Graphics 620