tashinz

this is the way I solved it:
just to remind what was the problem, TP700 out-of-box had firmware V15.0.0.x (x don't remember), in TIA Portal V19 I can only select TP700 V16.0.0.0 or V17.0.0.0. Just to mention, I've installed panel images V17 update 8 earlier. So I updated TP700 using ProSave to V17.0.0.8 which is what I have in Program Files\...\TIA Portal V19\...\V17\Images, why ProSave? Because TIA Portal said I don't have files to do Fit before project download. Now, I still cannot download project since in TP700 is in project is V17.0.0.0 (cannot change device to nothing else other than V16.0.0.0), and it asks to Fit operating system by downgrade, which I tried, but not possible since not having files...

so, I've downloaded image V17.0.0.0 from
Image Downloads for SIMATIC HMI Operator Panels: Comfort / Mobile / Basic Panels - ID: 109825750 - Industry Support Siemens

i.e. 
V17 109825750_ComfortPanels_V17.0.zip (204,9 MB)(SHA-256)

copied folder in zip file V17 to the path above, although it is not necessary, could have unzip it anywhere. Then I point ProSave to this folder (images\CP_7_9), and did update firmware. Now, TP700 has firmware V17.0.0.0, which is what is available in TIA Portal V19 project and now I can download my application.

spent two days to solve this thing. I got the message: buy Unified panels!

hope this is helpful to someone.

regards

 Downgrade SO in TP is the only way to match TIA Portal Runtime Version and HMI SO Image version.

Siemens must add newer versions on TIA Portal or at least add a comment on which version is required insted of recomend to upgrade to the newest.