According to the Canon Singapore website, the Canon Digital Photo Professional Express app for the iPad will require a monthly subscription fee from October 2019. The full details have not yet been released, with more to come soon. Right now, they just say that as of version 1.2.0, it will be subscription only.
Released in October last year, DPP Express has been a free app so far, for the iPad only. But with an App Store rating of only 1.6, it seems odd to suddenly make it subscription only. It is possible that this won’t happen for all regions, as it only appears to have shown up with Canon Singapore so far, but chances are, it’ll be global.