@Porknz 

Go to the TP Link website for your country and router. Select the support button, then the version number, then the firmware button.

  @ArcherC8  I can't find my router and I don't want to try to install the wrong firmware update.  What do I do if my router doesn't have a firmware update?

  @Porknz 

If I google tp link c5 it appears I get a different router than if I select the blue router name in your post. I assume this is not a US router. 

The US router has a version 1.20 in the support page. Do not load any firmware from a different country. 
 

Since this is an old router, if it were me, I would consider getting a newer model with at least AX wifi. They have more features and better wifi. I replaced an older router and an extender with a newer AX router and got better wifi speeds and distance. 
 

You can try a factory reset and reenter all your settings and/or do the normal things to trouble shoot the wifi such as different nodes, channels, and such. I prefer separate ssid names and allow ssid to be seen (do not hide). 

  @Porknz Is it a retail router or one provided by your ISP?  The link on your original post makes me think it's from your ISP.  Most of the time any firmware will have to come from them.  The date you show for the firmware you have is from April of 2024 so that's not too old.