Hi -we have an older version of soehnle 8310.00 baby scales for veterinary use. An E shows up on the screen now whenever we turn it on and nothing we do changes this. Is this fixable? Help!

There is nothing in the very basic manual

https://www.manua.ls/soehnle/venezia-65080/manual?p=2

But 'Out 2' points to condensation on the control board or buttons that need cleaning as mentioned here. Note though, it has a 5 year warranty.
https://www.ifixit.com/Answers/View/371285/The+LCD+screen+keeps+showing+OUT2+error+code

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Sometimes a CR2340 battery is still in it's package, but it may be very weak, even though it tests OK. Try another good battery.

try repeated pressure to reset (5-6 times in 10 sec) or could see if there is a small hole near battery compartment, push with paperclip (button reset)

suspect thats the battery - change it and see

Step 3: press and HOLD button "ON" next after starting the device! :)
https://www.manualslib.com/manual/1102838/Zelmer-34z015.html?page=28#manual

mcdevito75 here, You can try to disconnect the battery, then step on the scale then step off, Now re-install the battery and see how it works. If same contact scale manufacturer.

mcdevito75 here, There should be a button or knob close to the scale indicator you can press or turn to return the scale indicator to zero.

How to calibrate when "out2" is shown.
With the power off andthe scale on a stable surface, hold "g" and press "on". Some number will show up, probably a negative number. Press the "on" button again and the scale should display "Zero". Wait until it says "200.0". Gently place a 200 gram weight on the scale and wait a few seconds. If your successful it will say "Pass" and your scale will work again, yay!

http://www.fixya.com/support/r4964670-get_manual_most_any_electronic_device

I have looked and maybe you have the model number wrong the scale you are talking about 63700 Calando Quattrotronic scale is a simple digital scale and does not provide bmi, and hydration.
here is a link to the manual, http://www.leifheitusa.com/manual/63700.pdfit is in several languages including english as the company is european and sells to many countries. If you look english is there it is a very simple manual as the scale is only desinged to weight in either lbs or kgs nothing more. Sorry. If you would like a bmi chart you can get that here http://www.healthdiscovery.net/links/calculators/body_massindex_chart.htm and figure out your bmi based on height and weight in the chart.