General questions before I can really answer that:
- How many pages are in your project?
- Roughly how many gadgets on the page are displaying data from the customer's devices?
- What's the link speed like between the customer's browser and groov?
- Ditto for between groov and the devices?
- Is your customer doing anything that would inhibit caching in their browser? (e.g. Incognito mode, etc.)
Large numbers of pages and gadgets take a decent chunk of time to load. My primary test project here currently has 1,452 gadgets on it spread across 82 pages. A quick test on that one here shows about 3.5 seconds to parse all the pages out and do the initial page render, with the first data showing up 1-1.5 seconds later.
Lots of gadgets on a single page displaying data from devices is usually the biggest bottleneck. We batch requests up there in chunks of 20 tags to avoid overloading things, so it can take a bit for all gadgets to start showing data. (There are improvements coming down the pipeline soonish on this, though they won't be in the next release.)
Link speed always makes a difference, of course. Cellular data will take longer to load, etc. Older phones tend to be noticeably slower than newer ones. (My poor old iPad 2 struggles to even render groov nowadays.)