I have an online library access (in Austria). I can either access online my bookshelf via overdrive.com or libbyapp.com. The web access usually works fine but needs mobile data. There is also an Android app downloadable from the Aurora store called libbyapp. The advantage of the app is that you can hear to audio books also offline.
On my Sony Xperia XA2 plus I can run the app since sailfishos 4.x (and finally updated to sailfishos 5). I also got one of the C2 phones with sailfish 5. Here, I have already problems to open the app. I helps then to delete the cache - what is actually also offered by the app itself after a timeout reached. By reseting the app, I always use passwords and so on.
Once after reseting the app, I can access my bookshelf and may have online access to the audio book. I may even download the book succesfully, but then cannot open the audio book a second time.
Both phone connect to the same wlan, have the same microG version running. The C2 has an additional sd card and two sim cards. Usually mobile data are deactivated.
My feeling is that on the C2 the app misses some access rights on a folder. I had a similar problem with OsmAnd. When switched to SD card storage it downloaded the maps but never installed them. Internal storage works fine but is of course more limited.
How to check for such storage/cache problems? Is there any FOSS client, maybe even directly for SFOS?
Thanks.