I cannot reproduce this in Firefox or Chrome either by using the right click "Attributes..." menu option or by editing the font size in the right hand panel. Can you produce a screenshot and a description of the keystrokes you are using or maybe a video screencapture?

@andyfierman I can't use 5.5,4pt font size on firefox only. Minimum font size in EasyEDA in firefox is 6.5pt not 4pt.

Which editor? Schematic? Schematic lib? PCB? PCB lib? Is this with standard EasyEDA fonts or some font you have installed? You need to give more information as asked for earlier.

I have the same problem on Windows10 64 bit latest version ( Aug 2019). I was able to change the font at one point in a net but it did not carry across to another net an now having rebooted and started the app again, it will not change the font size on any change?

Edge is not supported. Please use Chrome or Firefox.

@paul_5011 Edge is not supported. Please use Chrome or Firefox. at v6.2.34 the net label font size can not be changed, it will be fixed at next release. thank you

Thanks to andyfierman and User Support. Thanks.  That worked. Paul