Lost backlinks following switch from http to https

[muzzmoz]

I have a client who appears to have taken a big hit in a few areas recently:

• MOZ Domain Authority has dropped from 16 to 1
• In ahrefs, their http version has 103 backlinks from 46 referring domains, but the https version shows 'no data' for backlinks or referring domains
• Their 'average position' in SERPs has fallen from around 32 to 43 in the last six weeks

Ininitally, I thought this might be due to the MOZ indexing problems last month.

However, I now suspect this is connected to their switch from http to https, which occured in mid December. Although all the http pages appear to be redirecting, it looks like the backlinks are not being associated to their https version.

Anyone had experience of this and/or now how to remedy?

[muzzmoz]

This issue just keeps getting murkier and murkier...

Even though ahrefs 'overview' reports 104 backlinks from 46 domains, when I go to The Best Pages by Backlinks, it says there are 691 results with a 429 Too Many Requests error.

Anyone know how to fix 429 errors on Shopify? Or even what causes them?