Certain apps can't connect to internet

Magnatolia · 14 Aug 2020

Hi all,

A while back my laptop wouldn't connect to the WiFi, however I got around this by connecting to my mobile phone's hotspot which utilises the phones connection to the main wifi.

Not sure if that's related, but I'm noticing certain apps act like I'm not on the internet. BitDefender won't update, can't load any free VPN applications, etc.

I managed to source this line from one of the free VPN application logs: "API request Login failed: DNS-resolution failed"

Yet my internet connection works fine. I can view websites, download files, etc.

Any thoughts on how to figure out the cause? Thanks!

dalchina · 14 Aug 2020

Hi, you might try:
Flush DNS Resolver Cache in Windows 10

then you could consider changing your DNS:
Change IPv4 and IPv6 DNS Server Address in Windows

DNSJumper (free) is quite good for this.

Check you're not using a proxy. (Internet properties, connections)

Magnatolia · 15 Aug 2020

Thanks @dalchina,

I flushed DNS cache, no luck.

I verified no proxy is being used.

I used DNS Jumper to change to Google's DNS, no change.

Anything else? I used to have a VPN service but that is completely uninstalled.

I'm noticing more apps that are functioning this way. Pretty much anytime an app tries to connect to the web to download an update or additional feature, it doesn't work. I have Iobit Advance Care and cannot even install additional features or updates.

I don't know if it's the problem, but I'm connecting my PC to the WiFi via my mobile phone's hotspot.

Is there a particular log in Windows, or a specific audit app, that can identify what's going on?

Cheers!
Thanks!

dalchina · 15 Aug 2020

Is there a difference if you create a new user for test purposes and log in as that user?
Or a clean boot? (Tutorial or Google if unsure how).

Have you created firewall rules - these can block ports or specific programs?

Have you used any so-called privacy software or perhaps ad-blocking software that creates rules in your Hosts file?

Iobit products seem not well-regarded but some.

Have you used a registry cleaner? (Don't!)

I wonder if you may have used some sort of 3rd party tool that has done this.

You could try tracking the activity of a particular process /program using e.g.
https://www.nirsoft.net/utils/live_tcp_udp_watch.html

If you can identify the ip address a particular program is attempting to access you could try to trace that, starting with 'ping'. E.g.
https://www.nirsoft.net/utils/multiple_ping_tool.html

This can help with issues of port access:
https://www.nirsoft.net/utils/cports.html

Magnatolia · 15 Aug 2020

I created a new user and something changed. As an example, when I loaded Advance Care it automatically provided a pop up advising that there was an update and it downloaded and updated 100%. However, when I went to install one of the extra features, it crashed. The second time, it showed 0% for the download and didn't do anything. I tested another application, which still didn't work. But the Advance Care update was definitely not working on my main account.

I reactivated my BitDefender Firewall rather than the Windows one, made sure the relevant software was enabled. I was not aware of any rules set up on Windows Firewall.

I wasn't aware of any ad blocking apps, but I did have one called AdGuard which I have uninstalled. Nothing changed. I also reviewed my Hosts file but there was nothing out of the ordinary.

I did use a reg cleaner just today, but was very cautious about what I selected.

I wasn't exactly sure how to use the tcp/udp watch program, but located the program I was having difficulties with, and pinged the IP address with 100% success for all 4 packets.

I ran the port util, but don't know what I'm meant to do with the information. One program creates 4 entries, the IP address of 1 is :: and the other is ::1, the other two have regular IP addresses. Not sure what to do with the ports?

Any other ideas? Thanks for your help!

dalchina · 15 Aug 2020

How many programs are you aware of that do not connect? Which are they?

Personally I wouldn't touch Advanced System Care or a registry cleaner- the latter should have nothing to do with your reported issue.

One possible reason for something not accessing the internet is a blocked port that it needs. For a good explanation see e.g.
How to Find Open and Blocked TCP/UDP Ports
and feel free to use Google yourself.

This article explains how you can check for open and blocked ports.
You may need to review that with respect to the particular program that cannot access the internet.

And again, there are various reasons access could be blocked or fail.

Remember to try a clean boot as well. (see above)

Magnatolia · 15 Aug 2020

Thanks! I managed to figure it out. Turns out, a while back, I had installed NetLimiter and decided not to use it so I terminated the app and disbled it from launching on startup. Unfortunately for me, it had installed a Windows Service that was still functioning without the parent app running.

Once I killed the service and permanently uninstalled the app, everything works fine!

Thanks again! Weirdly, I have no VPN active but every IP leak test I ran showed me with an IP address in a completely different state. Is this a benefit of using Google DNS?

Anyway, thanks again, really appreciate all the guidance and I now have a few more bits of knowledge under my belt!