Software Manager sometimes says "unable to download firmware updates" from a particular repository

When I open Ubuntu Software Manager on my machine, sometimes it returns this error:

Any idea about it?

I tried to delete the cache:

DNSSEC supported by current servers: no
Transactions
Current Transactions: 0 Total Transactions: 93545
Cache Current Cache Size: 4 Cache Hits: 3598 Cache Misses: 17357
DNSSEC Verdicts Secure: 0 Insecure: 0 Bogus: 0 Indeterminate: 0

and tried to change the server, trying different servers from US, Fr, Ch, Italy, and also trying the select better service option.

At my eyes, it looks like any server I choose, the IP address remains the same: 151.101.38.49

$ ping p2.shared.global.fastly.net

 PING p2.shared.global.fastly.net (151.101.38.49) 56(84) bytes of data. 64 bytes from 151.101.38.49 (151.101.38.49): icmp_seq=1 ttl=56 time=31.7 ms

This is my actual config:

2 Answers

As you say "sometimes** it returns this error"
It may be intermittent fault in your ISP server or site server. Run ping cdn.fwupd.org whenever you have the fault.This should be something like

ping cdn.fd.org
ping: cdn.fd.org: Name or service not known

otherwise

ping cdn.fwupd.org
PING p2.shared.global.fastly.net (151.101.194.49) 56(84) bytes of data.
64 bytes from 151.101.194.49 (151.101.194.49): icmp_seq=1 ttl=54 time=44.8 ms
64 bytes from 151.101.194.49 (151.101.194.49): icmp_seq=2 ttl=54 time=44.3 ms

If Software Manger shows error and ping is ok we can pssiblly try Software Manager server configuration.
To open Software & Updates run software-properties-gtk in terminal. In "Ubuntu Software" tab. Choosing some other server as shown below might help.

or maybe in Software & Update>Other Software>Canonical Partners is not selected. As below

Try this first:

1. Run sudo apt update to reload the list of software sources
2. If fwupd is not installed, install it using sudo snap install fwupd
3. Restart the computer
4. Open Ubuntu Software; the message should be gone

If the message is still there, you can try this:

1. Open Software & Updates (in 19.10 it's a white A on a blue background)
2. Select "Other" in the "Choose a server" dropdown
3. Click the "Select Best Server" button
4. When the dialog box closes, click the "Reload" button in the dialog asking about reloading the software information
5. Restart the computer