When installing your signature on gmail.com you might get an error that your signature is too long and to please try using a shorter signature. If this happens here a few things you can try:
First thing to try is during installation, make sure to click on open in new tab before you copy the signature to your clipboard. This prevents you from copying any elements that are not part of the signature.
If step one fails try these:
If you are suing more then 4 social media icons, try to remove a few.
If you have a disclaimer, try to make it shorter or remove it.
Try switching to the basic style as it uses less code then the other theme options