Having issues with calculating in custom character sheet

Hello everyone! I've been working on a custom character sheet and I've seemed to have run into an issue with my html, maybe someone can point out what I'm not seeing or understanding here. I essentially have my players Max HP be "(Constitution*2)+(Level*2)", but it's not outputting anything other than a blank square at all times. I've successfully done something similar with critical and dodge chances but I can't seem to locate the problem.

Script part in question:

Level: <input name="attr_level" type="number" value="0"> <br><br>
Max Health: <input name="attr_maxhp" type="number" value="(@{level}*2)+(@{constitution}*2)" disabled=true style="width:70px">
Constitution: <input name="attr_constitution" type="number" value="0"><button type="roll" value='/roll 1d20 + @{constitution}'></button>

And for comparison, the dodge/crit equations:

Critical Chance: <input name="attr_crit" type="number" value="(round(@{dexterity}*2))+@{excrit}" disabled=true><br><br>
Dodge: <input name="attr_dodge" type="number" value="(round(@{dexterity}*1.75))+@{exdodge}" disabled=true><button type="roll" value='/roll 1d100 + @{dodge}'></button><br><br>

Hi Diogo,

"but it's not outputting anything other than a blank square at all times."

What do you mean exactly?  If you call @{selected|maxhp} in chat do you get a value?  I'm guessing that you're referring to the token's max field for linking attributes?

the code looks fine in and of itself... but, a recommended practice for including an attribute's max value is to use "_max" appended to an existing attribute name ie name="attr_hp_max" so that linking tokens will automatically recognize the max value for the token bars.

So for example, you might have an input for HP @{hp} as

<input type="number" name="attr_hp" value="0" />

and it's max attribute @{hp|max} as 

<input type="number" name="attr_hp_max" value="(@{level}*2)+(@{constitution}*2)" disabled="true" />

I think that should solve a blank max field on linked token attributes.  If that's not the case... apologies if I misinterpreted the issue. ;-)

Problem ended up solving itself somewhat. Turns out it was just a preview sheet bug, as I tested some other functions in the sheet itself ingame, it was working as intended, thanks anyways tho!

"Preview"  Enough said.  ;-)

Diogo P. said:

Turns out it was just a preview sheet bug, as I tested some other functions in the sheet itself ingame, it was working as intended, thanks anyways tho!

Not as much a bug as a well-known problem with the preview, which is unreliable and should be trusted for checking anything than the most superficial changes.

Number 4 on the list: https://wiki.roll20.net/Building_Character_Sheets#Common_Mistakes