Hi there,

There are significant changes between versions Totara 12 and Totara TXP 13+, one of those areas being the technology stack used to deliver user interfaces, and by association the code used within Themes. Because of this, if you've created a custom Theme, you may need to touch code to be fully compatible. Here are some links to documentation on our technology changes on the front end, more specifically creating a custom theme in T13+, and a case study of our own experience upgrading this Community site from T12 to T13.

It's interesting that you've only noted that icons appear broken and nothing else though, that problem sounds quite specific. Have you purged the system caches as a first step, to uncache any stale files that might be hanging around? But also, if you have customised anything, then most notably perhaps from your brief description of the problem you're having, is the case study which describes upgrading CSS from LESS to SCSS.

In order to help further we will need some more details from you, such as understanding what you may have customised, for example have you customised the Basis or Roots themes?  Have you extended or changed the available icons? Also, I would encourage you or your Totara Partner to raise a support ticket, so that you can shared customised code with us etc.

Kind regards,

Dave