I cannot download any attachment with Gmail (Part 1)

What the heck is going on?  I've been having on and off problems with downloading attachments from gmail recently.  It sometime works, sometimes not.

Now it looks like the download button stopped functioning altogether.  It does't work with the Download button on the attachment as part of the message, it does't work with the download button after opening the attached document by clicking on it.

I can Add to Google Drive and then download from there, but that's a waste of time.

Ideas?

I'm on Mac Yosemite 10.10.5, Safari 10.0


---
UPDATE!  I found the answer and culprit(s): freaking Safari Plug-ins! 
---
UPDATE!  NOPE! - I thought that was the problem, but it is NOT.  I CAN'T download any attachment. Read on if you want, but that stuff below didn't fix the problem.

Go to: Safari / Preferences / Security

There is a box for Internet plug-ins, I turned OFF "Allow Plug-ins", and bam! I can download attachments just fine.

 When "Allow Plug-ins is checked, one can click onto Plug-in Settings and you get to see what's there, what's allowed to run or not, and make changes.

But darn it! With 8 Plug-ins installed already and hundreds of websites, forget it!  I'm not tweaking these by hand. I think I'll simply delete them all and re-install with an eye on it.
---
To remove Safari plug-ins: Go to 

• /Library/Internet Plug-Ins/
• ~/Library/Internet Plug-Ins/

https://support.apple.com/kb/PH19241?locale=en_US&viewlocale=en_US

---
Interesting info from Safari help:


Allow Plug-ins

Let Safari show plug-in content on websites.

Websites use plug-ins for pictures, music, video, animation, interactive features, and other enhancements. Some plug-ins track your browsing history.

Click Plug-in Settings to see which plug-ins are installed, disable or enable plug-ins, see which websites you visited use each plug-in, and set blocking policies for plug-in use.

To disable or enable an installed plug-in, deselect or select the checkbox to the left of the plug-in name.

To set a blocking policy for a visited website that uses a plug-in, select the plug-in on the left, select the website on the right, then click its pop-up menu and choose a policy:

• Ask: When you visit the website, Safari displays a placeholder instead of the plug-in content. You can click the placeholder to allow the website to use the plug-in.
• Off: When you visit the website, Safari will first attempt to load content without using a plug-in. If a site still requires a plug-in, Safari displays a placeholder instead of the plug-in content.
• On: Safari lets the website use the plug-in, unless it’s blocked by macOS File Quarantine. For more information, see the Apple Support article About the "Are you sure you want to open it?" alert.
• Enable Security Protection: Safari prevents the website from using the plug-in if it’s blocked by macOS File Quarantine. To run the plug-in, hold down the Option key, click the plug-in’s pop-up menu, and deselect Enable Security Protection. Deselecting Enable Security Protection may present a security risk, so choose this option only for a website you trust.
• Run in Safe Mode: Safari lets the website use the plug-in but runs malware checks. To run the plug-in outside of Safe Mode, hold down the Option key, click the plug-in’s pop-up menu, and deselect Run in Safe Mode. Deselecting Run in Safe Mode may present a security risk, so choose this option only for a website you trust.

To set the blocking policy for other websites that use a plug-in, select the plug-in on the left, then click the “When visiting other websites” pop-up menu and choose an option described above.